Chain drive tensioner spring force control mechanism

ABSTRACT

A tensioner which adjusts the mean tensioner force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency as the chain wears and is subject to low dynamic loads.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending application Ser. No.15/146,472, filed May 4, 2016, entitled, “CHAIN DRIVE TENSIONER SPRINGFORCE CONTROL MECHANISM”, which is a divisional of application Ser. No.14/196,261, filed Mar. 4, 2014, entitled “CHAIN DRIVE TENSIONER SPRINGFORCE CONTROL MECHANISM”, which claims priority from InternationalApplication No. PCT/US2012/053830, entitled “CHAIN DRIVE TENSIONERSPRING FORCE CONTROL MECHANISM, which was filed on Sep. 6, 2012, whichclaims the benefit of Provisional Application No. 61/537,651, entitled,“CHAIN DRIVE TENSIONER SPRING FORCE CONTROL MECHANISM, filed Sep. 22,2011; and also claims priority from International Application No.PCT/US2014/019329, entitled, “CHAIN DRIVE TENSIONER SPRING FORCE CONTROLMECHANISM filed Feb. 28, 2014. This application also claims the benefitof Provisional Application No. 61/772,673 filed Mar. 5, 2013, entitled“CHAIN DRIVE TENSIONER SPRING FORCE CONTROL MECHANISM”. Theaforementioned applications are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention pertains to the field of tensioners. More particularly,the invention pertains to chain drive tensioner spring force controlmechanisms.

Description of Related Art

Generally, in timing chains for valve drives of internal combustionengines, camshaft chains in use for a camshaft-camshaft drive, andbalancer chains, have tensioners that are used on the slack side of achain to take up slack in the chain and to apply tension to the chain.

During operation, a piston of the tensioner presses against the chain tomaintain tension in the chain. When tension in the chain increasesduring operation due to resonance of a chain span, a high load from thechain acts on the piston of the tensioner, causing the piston to retractinto the housing of the tensioner.

Chain drive tensioner spring force is often too high for most operatingconditions so that the spring force is sufficient to handle worst caseoperating conditions of the tensioner system. The effectiveness of thetensioner and the overall system behavior and efficiency could beimproved if the tensioner spring force could be varied with operatingconditions taking into account wear and stretching that occurs in thechain during the life of the chain.

SUMMARY OF THE INVENTION

A tensioner which adjusts the mean tensioner force to keep the chaintension as low as possible without sacrificing chain control,significantly improving drive efficiency as the chain wears and issubject to low dynamic loads.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1a shows a schematic of a tensioner of a passive tensioner systemtensioning a new chain. FIG. 1b shows a schematic of a tensionertensioning a worn chain without high loads. FIG. 1c shows a schematic oftensioner tensioning a worn chain with high load.

FIG. 2 shows a schematic of a tensioner of a passive tensioner systemtensioning a new chain.

FIG. 3 shows a schematic of a tensioner of a passive tensioner systemtensioning a new chain.

FIG. 4 shows a schematic of a tensioner of a passive tensioner systemusing chambers formed between an outer circumferential flange of amoveable sleeve and a bore flange of the housing to maintain theposition of the moveable sleeve relative to the piston to tension a newchain.

FIG. 5 shows a schematic of a tensioner of a passive tensioner systemusing chambers formed between a bore flange of the housing and a cutouton the outer circumference of the moveable sleeve to maintain theposition of the moveable sleeve relative to the piston to tension a newchain.

FIG. 6 shows a schematic of a tensioner of a passive tensioner systemusing chambers formed between the outer circumferential flange of amoveable sleeve and the bore of the housing to maintain the position ofthe moveable sleeve relative to the piston to tension a new chain.

FIG. 7 shows a schematic of a tensioner of a passive tensioner systemusing chambers formed between the an outer circumferential flange of amoveable sleeve and a bore flange of the housing supplied by a spoolvalve to maintain the position of the moveable sleeve relative to thepiston to tension a new chain.

FIG. 8 shows a schematic of a tensioner of a passive tensioner systemusing chambers formed between the an outer circumferential flange of amoveable sleeve and a bore of the housing supplied by a spool valve andan accumulator to maintain the position of the moveable sleeve relativeto the piston to tension a new chain.

FIG. 9 shows a schematic of a tensioner of an active tensioner systemusing a feedback control to move and maintain a moveable sleeve relativeto a piston to tension a new chain.

FIG. 10 shows a schematic of a tensioner of an active tensioner systemusing feedback control to move a moveable sleeve relative to a piston totension a new chain.

FIG. 11a shows a schematic of a tensioner of a tensioner systemtensioning a new chain. FIG. 11b shows a schematic of a tensionertensioning a worn chain without high loads. FIG. 11c shows a schematicof tensioner tensioning a worn chain with high load.

FIG. 12a shows a schematic of a tensioner tensioning a new chain. FIG.12b shows a schematic of a tensioner tensioning a worn chain withouthigh loads. FIG. 12c shows a schematic of tensioner tensioning a wornchain with high load.

FIG. 13a shows a schematic of a tensioner tensioning a new chain. FIG.13b shows schematic of a tensioner tensioning a worn chain without highloads. FIG. 13c shows a schematic of tensioner tensioning a worn chainwith high load.

FIG. 14a shows a schematic of a tensioner tensioning a new chain. FIG.14b shows schematic of a tensioner tensioning a worn chain without highloads. FIG. 14c shows a schematic of tensioner tensioning a worn chainwith high load.

FIG. 15 shows a schematic of a tensioner tensioning a new chain.

FIG. 16 shows a schematic of a tensioner tensioning an endless chainthrough an arm.

FIG. 17 shows an alternate view of a tensioner tensioning an endlesschain through an arm.

FIG. 18a shows a schematic of a tensioner tensioning a new chain. FIG.18b shows schematic of a tensioner tensioning a worn chain without highloads. FIG. 18c shows a schematic of tensioner tensioning a worn chainwith high load.

FIG. 19a shows a schematic of a tensioner tensioning a new chain. FIG.19b shows a schematic of a tensioner tensioning a worn chain withouthigh loads. FIG. 19c shows a schematic of a tensioner tensioning a wornchain with high load.

FIG. 20a shows a schematic of a tensioner tensioning a new chain. FIG.20b shows a schematic of a tensioner tensioning a worn chain withouthigh loads. FIG. 20c shows a schematic of a tensioner tensioning a wornchain with high load.

FIG. 21a shows a schematic of a tensioner tensioning a new chain. FIG.21b shows a schematic of a tensioner tensioning a worn chain withouthigh loads. FIG. 21c shows a schematic of a tensioner tensioning a wornchain with high load.

FIG. 22a shows a schematic of a tensioner tensioning a new chain. FIG.22b shows a schematic of a tensioner tensioning a worn chain withouthigh loads. FIG. 22c shows a schematic of a tensioner tensioning a wornchain with high load

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1a -8, 11-15, and 18 a-22 c show tensioner systems using passivecontrol to maintain the position of a moveable sleeve relative to apiston. Passive control is defined as a system in which no feedback isused to regulate the position of a movable sleeve relative to a pistonof the tensioner. In contrast, FIGS. 9 and 10 are active control systemsin which real time feedback of components of the engine and/or themoveable sleeve itself are used to regulate the position of the sleeve.

The tensioner systems includes a tensioner (described in further detailbelow) for a closed loop chain drive system used in an internalcombustion engine. It may be utilized on a closed loop powertransmission system between a driveshaft and at least one camshaft or ona balance shaft system between the driveshaft and a balance shaft. Thetensioner system may also include an oil pump and be used with fuel pumpdrives. Additionally, the tensioner systems may also be used with beltdrives. The piston or external piston of the tensioner may tension thechain 350 or belt through an arm 352 as shown in FIGS. 16-17.

FIGS. 1a-1c show the tensioner tensioning under various chainconditions; FIG. 1a is tensioning a new chain; FIG. 1b is tensioning aworn chain without high loads; FIG. 1c is tensioning a worn chain underhigh load.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with first diameterportion D1 and a second diameter portion D2, with the second diameterportion D2 being larger than the first diameter portion D1.

Received within the bore 2 a of the housing 2 is a moveable sleeve 18.The moveable sleeve 18 is hollow and forms a pressure chamber 16 with apressure P1 with the bore 2 a of the housing 2, the inner diameterportion 17 or the hollow interior of the hollow moveable sleeve 18, andthe interior 3 a of the piston 3.

A sleeve spring 5 is present within the bore 2 a and is received withinthe inner diameter portion 17 of the moveable sleeve 18, with a firstend 5 a of the sleeve spring 5 in contact with a bottom surface 24 ofthe inner flange 22 of the moveable sleeve 18 and second end 5 b of thesleeve spring 5 in contact with the bottom 2 c of the bore 2 a. Thesleeve spring 5 provides a bias force to reduce the control forcerequired to keep the moveable sleeve 18 in the desired position relativeto the piston 3.

The moveable sleeve 18 has an outer circumferential flange 20, whichincreases the diameter of the moveable sleeve 18 to be approximatelyequal to the diameter of the second diameter portion D2, but allowingthe flange 20 to slide within the second diameter portion D2 of the bore2 a and to form a fluid chamber 14 between the bottom surface 27 of theouter circumferential flange 20 and the second diameter portion D2 ofthe bore 2 a. The fluid chamber 14 is in fluid communication with an oilpressure supply 7 through a supply line 12 containing a check valve 10.The supply 7 supplies fluid to the fluid chamber 14 to make up for anyleakage that may occur. The check valve 10 prevents any fluid in thefluid chamber 14 from entering back into the supply 7. It should benoted that fluid pressure is not supplied to the area between topsurface 29 of the outer circumferential flange 20 and the bore 2 a.

At least a portion of the moveable sleeve 18 forward of the outercircumferential flange 20 is slidably received within the hollow piston3. Also present within the hollow piston 3 is a piston spring 4 biasingthe piston 3 outwards from the housing 2. The piston spring 4 has afirst end 4 a in contact with the interior 3 a of the hollow piston 3and a second end 4 b in contact with a top surface 26 of the innerflange 22 of the moveable sleeve 18. A through hole 25 is present in theinner flange 22 allowing fluid from the inlet supply line 6 to interior3 a of the piston 3 and the top surface 26 of the inner flange 22 of themoveable sleeve 18.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. The supply 7 providing fluid to the fluid chamber14 may be the same as the supply providing fluid to inlet supply line 6.Alternatively, the supply supplying fluid to the inlet supply line 6 maybe different than the supply 7 in fluid communication with fluid chamber14. Furthermore, a vent or pressure relief valve (not shown) may bepresent within the hollow piston 3.

Referring to FIG. 1a , when the tensioner is tensioning a new chain,during operation, fluid is supplied to the hydraulic chamber 16 from aninlet supply line 6 and optionally through an inlet check valve topressurize the hydraulic chamber 16 and bias the piston 3 outward fromthe housing 2 in addition to the spring force from piston spring 4, tobias a span of the closed loop chain.

Referring to FIG. 1b , when the tensioner is tensioning a worn chain,without high load, during operation, fluid is supplied to the hydraulicchamber 16 from an inlet supply line 6 and optionally through an inletcheck valve (not shown) to pressurize the hydraulic chamber 16 and biasthe piston 3 outward from the housing 2 in addition to the spring forcefrom piston spring 4, to bias a span of the closed loop chain. As thechain wears, the piston 3 has to be biased further outwards from thehousing 2 in order to adequately tension the chain. As a greater amountof fluid is required to add the spring force in biasing the piston 3outwards from the housing 2, some of the fluid supplied to the hydraulicchamber 16 leaks to the fluid chamber 14 and moves the moveable sleeve18 outwards from the housing 2. It should be noted that the movablesleeve 18 is moved outwards mostly by oil from supply 7 and not the oilfrom hydraulic chamber 16.

Referring to FIG. 1c , when the tensioner is tensioning a worn chainduring high chain load, during operation, the high force pushes thepiston 3 inwards towards the housing 2 from the piston position shown inFIG. 1b (indicated by dashed lines). The inward force and motion of thepiston 3 is resisted by the fluid in fluid chamber 14, since the checkvalve 10 in supply line 12 blocks and fluid from exiting fluid chamber14, essentially pressurizing the fluid chamber 14. The pressurization ofthe fluid chamber 14 causes the inner flange 22 of the moveable sleeve18 to exert an outward force on the piston 3 through the piston spring4, opposing the inward force. Once the high load is removed from thepiston 3, essentially depressurizing the chamber 14, supply 7 suppliesfluid through the check valve 10 and supplies fluid to the fluid chamber14 to fill the fluid chamber 14 and compensate for the movement of thesleeve 18 relative to the piston 3 and to maintain the position of thesleeve 18 relative to the piston 3.

Movement of the moveable sleeve 18 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

Seals (not shown) may be present between the outer circumferentialflange 20 and the moveable sleeve 18 and between the second diameterportion D2 of the bore 2 a and the first diameter of the bore D1 or anyother place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16and fluid chamber 14 of the tensioner and substantially prevents inwardmovement of piston 3 and the moveable sleeve 18 towards the housing 2when the chain span is under load.

FIG. 2 shows a tensioner for a passive tensioner system using supplypressure to move a moveable sleeve 33 received by the hollow piston 3.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with a firstdiameter portion D1 and a second diameter portion D2, with the seconddiameter portion D2 being larger than the first diameter portion D1.

A hollow moveable sleeve 33 is received within the bore 2 a of thehousing 2. Received within the hollow moveable sleeve 33 is a hollowfixed sleeve 30. Within the hollow fixed sleeve 30 is sleeve spring 5.The first end 5 a of the sleeve spring 5 is in contact with a bottomsurface 36 of an inner flange 34 of the moveable sleeve 33 and thesecond end 5 b of the sleeve spring 5 is in contact with a bottomsurface 32 of an inner flange 31 of the hollow fixed sleeve 30 or bottomof the bore 2 c, if no flange 31 is present. The sleeve spring 5provides a bias force to reduce the control force required to keep themoveable sleeve 33 in the desired position relative to the piston 3. Apressure chamber 16 is formed between an inner diameter portion 38 ofthe fixed sleeve 30, the inner diameter portion 17 of the hollowinterior of the hollow moveable sleeve 33, and the interior 3 a of thepiston 3.

The moveable sleeve 33 has a diameter which is approximately equal tothe diameter of the second diameter portion D2, but still allows themoveable sleeve 33 to slide within the bore 2 a. A fluid chamber 37 isformed between a bottom 2 c of the bore 2 a, the fixed sleeve 30 and abottom end surface 39 of the moveable sleeve 33. The fluid chamber 37 isin fluid communication with an oil pressure supply 7 through a supplyline 12 containing a check valve 10. The supply 7 supplies fluid to thefluid chamber 37 to make up for any leakage that may occur. The checkvalve 10 prevents any fluid in the fluid chamber 37 from entering backinto the supply 7. It should be noted that fluid pressure is notsupplied to the area between the piston 3, the moveable sleeve 33 andthe second diameter portion D2 of the bore 2 a.

At least a portion of the moveable sleeve 33 is slidably received withinthe hollow piston 3. Also present within the hollow piston 3 is a pistonspring 4 biasing the piston 3 outwards from the housing 2. The pistonspring 4 has a first end 4 a in contact with the inner portion 3 a ofthe hollow piston 3 and a second end 4 b in contact with a top surface35 of the inner flange 34 of the moveable sleeve 33. A through hole 25is present in the inner flange 34 allowing fluid from the inlet supplyline 6 to the interior 3 a of the piston and the top surface 35 of theinner flange 34 of the moveable sleeve 33.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. The supply 7 providing fluid to the fluid chamber37 may be the same as the supply providing fluid to inlet supply line 6.Alternatively, the supply supplying fluid to the inlet supply line 6 maybe different than the supply 7 in fluid communication with fluid chamber37. Furthermore, a vent or pressure relief valve (not shown) may bepresent within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the hydraulic chamber 16 from an inlet supply line 6 andoptionally through an inlet check valve (not shown) to pressurize thehydraulic chamber 16 and bias the piston 3 outward from the housing 2 inaddition to the spring force from piston spring 4, to bias a span of theclosed loop chain similar to FIG. 1 a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the hydraulic chamber 16 from an inletsupply line 6 and optionally through an inlet check valve to pressurizethe hydraulic chamber 16 and bias the piston 3 outward from the housing2 in addition to the spring force from piston spring 4, to bias a spanof the closed loop chain. As the chain wears, the piston 3 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. As a greater amount of fluid is required to add thespring force in biasing the piston 3 outwards from the housing 2, someof the fluid supplied to the hydraulic chamber 16 leaks to the fluidchamber 37 between the moveable sleeve 33, the fixed sleeve 30, and thebore 2 a of the housing and moves the moveable sleeve 33 outwards fromthe housing 2, similar to FIG. 1b . It should be noted that the movablesleeve is moved outwards mostly by oil from supply 7 and not the oilfrom hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 3 inwards towards thehousing 2 from the piston position shown in FIG. 1c (indicated by dashedlines). The inward force and motion of the piston 2 is resisted by thefluid in fluid chamber 37, since the check valve 10 in supply line 12blocks fluid from exiting fluid chamber 37, essentially pressurizing thechamber 37. The pressurization of the fluid chamber 37 causes the innerflange 34 of the moveable sleeve 33 to exert an outward force on thepiston 3 through the piston spring, opposing the inward force. Once thehigh load is removed from the piston 3, essentially depressurizing thechamber 37, supply 7 supplies fluid through the check valve 10 andsupplies fluid to the fluid chamber 37 to fill the fluid chamber 37 andcompensate for the movement of the sleeve 33 relative to the piston 3and to maintain the position of the sleeve 33 relative to the piston 3.

Movement of the moveable sleeve 33 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

Seals (not shown) may be present between the moveable sleeve 33 and thebetween the second diameter portion D2 of the bore 2 a and the seconddiameter portion D2 and the first diameter of the bore D1 or any otherplace within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16and fluid chamber 37 of the tensioner and substantially prevents inwardmovement of piston 3 and the moveable sleeve 33 towards the housing 2when the chain span is under load.

FIG. 3 shows a tensioner for a passive tensioner system using supplypressure to move a moveable sleeve 40 which receives a hollow piston 3.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. Received within the bore 2 a of the housing 2 is amoveable sleeve 40. The moveable sleeve 40 has a first opening 46 adefined by a top inner diameter portion 46 and a top surface 43 ofcentral inner flange 41 and a second opening 45 a defined by a bottominner diameter portion 45 and a bottom surface 42 of central innerflange 41. A through hole 47 of the central inner flange 41 connects thefirst opening 46 a to the second opening 45 a of the moveable sleeve 40.A top surface 48 of the moveable sleeve 40 is exposed to atmosphericpressure.

Received within the first opening 46 a of the moveable sleeve 40,defined by the top inner diameter portion 46 and the top surface 43 ofthe central inner flange 41 is a hollow piston 3. Within the hollowpiston 3 is a piston spring 4 biasing the piston 3 outwards from thehousing 2. The piston spring 4 has a first end 4 a in contact with theinner portion 3 a of the hollow piston 3 and a second end 4 b in contactwith a top surface 43 of the central inner flange 41 of the moveablesleeve 40.

Received within the second opening 45 a of the moveable sleeve 40,defined by the bottom inner diameter portion 45 and the bottom surface42 of the central inner flange 41 is a hollow fixed sleeve 30. Withinthe hollow fixed sleeve 30 is sleeve spring 5. The first end 5 a of thesleeve spring 5 is in contact with a bottom surface 42 of the centralinner flange 41 of the moveable sleeve 40 and the second end 5 b of thesleeve spring 5 is in contact with a bottom surface 32 of an innerflange 31 of the hollow fixed sleeve 30. The sleeve spring 5 provides abias force to reduce the control force required to keep the moveablesleeve 40 in the desired position relative to the piston 3. A pressurechamber 16 is formed between an inner portion 38 of the fixed sleeve 30,or bottom of the bore if a flange 31 is not present, the inner diameterportion 17 of the second opening 45 a of the moveable sleeve 40, and theinterior 3 a of piston 3. The through hole 47 is present in the centralinner flange 41 allows fluid from the inlet supply line 6 to theinterior 3 a of the piston and the top surface 43 of the central innerflange 41 of the moveable sleeve 40.

A fluid chamber 37 is formed between a bottom of the bore 2 a, the fixedsleeve 30 and a bottom end surface 39 of the moveable sleeve 40. Thefluid chamber 37 is in fluid communication with an oil pressure supply 7through a supply line 12 containing a check valve 10. The check valve 10prevents any fluid in the fluid chamber 37 from entering back into thesupply 7.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. The supply 7 providing fluid to the fluid chamber37 may be the same as the supply providing fluid to inlet supply line 6.Alternatively, the supply supplying fluid to the inlet supply line 6 maybe different than the supply 7 in fluid communication with fluid chamber37. Furthermore, a vent or pressure relief valve (not shown) may bepresent within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the hydraulic chamber 16 from an inlet supply line 6 andoptionally through an inlet check valve to pressurize the hydraulicchamber 16 and bias the piston 3 outward from the housing 2 in additionto the spring force from piston spring 4, to bias a span of the closedloop chain similar to FIG. 1 a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the hydraulic chamber 16 from an inletsupply line 6 and optionally through an inlet check valve to pressurizethe hydraulic chamber 16 and bias the piston 3 outward from the housing2 in addition to the spring force from piston spring 4, to bias a spanof the closed loop chain. As the chain wears, the piston 3 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. As a greater amount of fluid is required to add thespring force in biasing the piston 3 outwards from the housing 2, someof the fluid supplied to the hydraulic chamber 16 leaks to the fluidchamber 37 between the moveable sleeve 33 and the fixed sleeve 30 andmoves the moveable sleeve 40 outwards from the housing similar to FIG.1b . It should be noted that the movable sleeve is moved outwards mostlyby oil from supply 7 and not the oil from hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 3 inwards towards thehousing from the piston position shown in FIG. 1c (indicated by dashedlines). The inward force and motion of the piston is resisted by thefluid in fluid chamber 37, since the check valve 10 in supply line 12blocks fluid from exiting fluid chamber 37, essentially pressurizing thefluid chamber 37. The pressurization of the fluid chamber 37 causes thecentral inner flange 41 of the moveable sleeve 40 to exert an outwardforce on the piston 3 through the piston spring 4, opposing the inwardforce.

Once the high load is removed from the piston 3, essentiallydepressurizing the chamber 37, supply 7 supplies fluid through the checkvalve 10 and supplies fluid to the fluid chamber 37 to fill the fluidchamber 37 and compensate for the movement of the sleeve 40 relative tothe piston 3 and to maintain the position of the sleeve 40 relative tothe piston 3.

Movement of the moveable sleeve 40 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 40 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16,and fluid chamber 37 of the tensioner and substantially prevents inwardmovement of piston 3 and the moveable sleeve 40 towards the housing 2when the chain span is under load.

FIG. 4 shows a tensioner for a passive tensioner system using supplypressure to move a moveable sleeve received by a hollow piston 3.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with a firstdiameter portion D1 and a second diameter portion D2, with the seconddiameter portion D2 being larger than the first diameter portion D1. Abore flange 150 separates a second diameter portion D2 of the bore 2 athat receives the piston 3 and another second diameter portion D2 of thebore that receives an outer circumferential flange 141 of the moveablesleeve 140.

Received within the bore 2 a of the housing 2 is a moveable sleeve 140.The moveable sleeve 140 is hollow and forms a pressure chamber 16 withthe bore 2 a of the housing 2, the inner diameter portion 17 of thehollow moveable sleeve 140, and the interior 3 a of the piston 3. Asleeve spring 5 is present within the bore 2 a and is received withinthe inner diameter portion 17 of the moveable sleeve 140, with a firstend 5 a of the spring 5 in contact with a bottom surface 147 of theinner flange 145 of the moveable sleeve 140 and second end 5 b of thespring 5 in contact with the bottom 2 c of the bore 2 a. The sleevespring 5 provides a bias force to reduce the control force required tokeep the moveable sleeve 140 in the desired position relative to thepiston 3.

The moveable sleeve 140 has an outer circumferential flange 141 with atop surface 142 with an area A2 and a bottom surface 143 with an areaA1. The area A2 of the top surface 142 is less than the area A1 of thebottom surface 143. A first fluid chamber 58 is formed between a topsurface 142 of the outer circumferential flange 141 and the bottomsurface 152 of the bore flange 150 and a second fluid chamber 57 betweenthe bottom surface 143 of the outer circumferential flange 141 andanother wall 73 of the second diameter portion D2.

The first fluid chamber 58 is connected to a supply 7 through line 55,which preferably has a check valve 53 and the second fluid chamber 57 isconnected to a supply 7 through line 56, which also preferably has acheck valve 54. The check valves 53, 54 prevent any fluid in the fluidchambers 58, 57 from entering back into supply 7. The supply 7 suppliesfluid to the fluid chambers 58, 57 to make up for any leakage that mayoccur.

At least a portion of the moveable sleeve 140 forward of the outercircumferential flange 141 is slidably received within the hollow piston3. Also present within the hollow piston 3 is a piston spring 4 biasingthe piston 3 outwards from the housing 2. The piston spring 4 has afirst end 4 a in contact with the inner portion 3 a of the hollow piston3 and a second end 4 b in contact with a top surface 146 of the innerflange 145 of the moveable sleeve 140. A through hole 144 is present inthe inner flange 145 allowing fluid from the inlet supply line 6 to theinterior 3 a of the piston and the top surface 146 of the inner flange145 of the moveable sleeve 140.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. The supply 7 providing fluid to the fluid chambers57, 58 may be the same as the supply providing fluid to inlet supplyline 6. Alternatively, the supply supplying fluid to the inlet supplyline 6 may be different than the supply 7 in fluid communication withfluid chambers 57, 58. Furthermore, a vent or pressure relief valve (notshown) may be present within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the hydraulic chamber 16 from an inlet supply line 6 andoptionally through an inlet check valve to pressurize the hydraulicchamber 16 and bias the piston 3 outward from the housing 2 in additionto the spring force from piston spring 4, to bias a span of the closedloop chain similar to FIG. 1 a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the hydraulic chamber 16 from an inletsupply line 6 and optionally through an inlet check valve to pressurizethe hydraulic chamber 16 and bias the piston 3 outward from the housing2 in addition to the spring force from piston spring 4, to bias a spanof the closed loop chain. As the chain wears, the piston 3 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. As a greater amount of fluid is required to add thespring force in biasing the piston 3 outwards from the housing 2, someof the fluid supplied to the hydraulic chamber 16 leaks to the fluidchambers 57, 58 between the moveable sleeve 140 and bore 2 a of thehousing. It should be noted that the movable sleeve 140 is movedoutwards mostly by oil from supply 7 and not the oil from hydraulicchamber 16. Since a bottom surface 143 of the outer circumferentialflange 141 has a greater area A1 than the area A2 of the top surface 142of the outer circumferential flange 141, chamber 57 requires less fluidpressure to move the moveable sleeve 140 outwards from the housingsimilar to FIG. 1b , than chamber 58 to move the moveable sleeve 140 inthe opposite direction.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 3 inwards towards thehousing 2 from the piston position shown in FIG. 1c (indicated by dashedlines). The inward force and motion of the piston 3 is resisted by thefluid in fluid chamber 57 since the check valve 54, in supply line 56blocks fluid from exiting the fluid chamber 57, essentially pressurizingthe fluid chamber 57. Furthermore, with the area A1 of the bottomsurface 143 of circumferential flange 141 being greater than the area A2of the top surface 142 of the circumferential flange 141, thepressurization of the fluid chamber 57 causes the inner flange 145 ofthe moveable sleeve 33 to be “pumped” up or move the moveable sleeve 140outward from the housing 2 and exert an outward force on the piston 3through the piston spring 4, opposing the inward force. Once the highload is removed from the piston 3, essentially depressurizing the fluidchamber 57, supply 7 supplies fluid through the check valve 54 andsupplies fluid to the fluid chamber 57 to fill the fluid chamber 57 andcompensates for the movement of the sleeve 140 relative to the piston 3and to maintain the position of the sleeve 140 relative to the piston 3.

Movement of the moveable sleeve 140 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

It should be noted that when fluid chamber 57 is depressurizing, fluidchamber 58 is pressurizing. The filling of fluid chamber 57 with fluidfrom supply 7 moves the moveable sleeve 140. The movement of themoveable sleeve 140 beyond or greater than the travel necessary tomaintain the position of the piston 3 relative to the chain is resistedby the fluid in fluid chamber 58 since the check valve 53, in supplyline 55 block fluid from exiting the fluid chamber 58, essentiallypressurizing the chamber 58. Once the load is removed from the sleeve,the chamber 58 depressurizes and supply 7 supplies fluid through thecheck valve 53 and supplies fluid to the fluid chamber 58 to fill thechamber 58 and compensates for movement of the sleeve 140 relative tothe piston 3 and maintains the position of the sleeve 140 relative tothe piston regardless of other forces acting on sleeve.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 140 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by pressure chamber 16and fluid chambers 57, 58 of the tensioner and substantially preventsinward movement of piston 3 and the moveable sleeve 140 towards thehousing 2 when the chain span is under load.

FIG. 5 shows a tensioner for a passive tensioner system using supplypressure to move a moveable sleeve received by a piston.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. Received within the bore 2 a of the housing 2 is amoveable sleeve 163. The moveable sleeve 163 is hollow and forms apressure chamber 16 with the bore 2 a of the housing 2, the innerdiameter portion 169 of the hollow moveable sleeve 163, and the interior3 a of the piston 3.

A sleeve spring 5 is present within the bore 2 a and is received withinthe inner diameter portion 169 of the moveable sleeve 163, with a firstend 5 a of the spring 5 in contact with a bottom surface 166 of theinner flange 164 of the moveable sleeve 163 and second end 5 b of thespring 5 in contact with the bottom 2 c of the bore 2 a. The sleevespring 5 provides a bias force to reduce the control force required tokeep the moveable sleeve 163 in the desired position relative to thepiston 3.

Along an outer circumferential portion of the moveable sleeve 163 is acircumferential cutout 168. The cutout 168 of the moveable sleeve 163slidably receives a bore flange 160. The bore flange 160 has a topsurface 161 with an area A1 and a bottom surface 162 with an area A2.The area A1 of the top surface 161 of the bore flange 160 is greaterthan the area A2 of the bottom surface 162 of the bore flange 160.

A first fluid chamber 58 is formed between a top surface 161 of the boreflange 160 and the cutout 168 surface of the moveable sleeve 163 and asecond fluid chamber 57 is formed between the bottom surface 162 of thebore flange 160 and another surface of the cutout 168 of the moveablesleeve 163. The first fluid chamber 58 is connected to a supply 7through line 55, which preferably has a check valve 53 and the secondfluid chamber 57 is connected to a supply 7 through line 56, which alsopreferably has a check valve 54. The check valves 53, 54 prevent anyfluid in the fluid chambers 58, 57 from entering back into supply 7.Supply 7 provides fluid to the fluid chambers 57, 58 to make up for anyleakage that occurs.

At least a portion of the moveable sleeve 163 forward of the cutout 168is slidably received within the hollow piston 3. Also present within thehollow piston 3 is a piston spring 4 biasing the piston 3 outwards fromthe housing 2. The piston spring 4 has a first end 4 a in contact withthe interior 3 a of the hollow piston 3 and a second end 4 b in contactwith a top surface 165 of the inner flange 164 of the moveable sleeve163. A through hole 144 is present in the inner flange 164 allowingfluid from the inlet supply line 6 to the interior 3 a of the piston andthe top surface 165 of the inner flange 164 of the moveable sleeve 163.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. The supply 7 providing fluid to the fluid chambers57, 58 may be the same as the supply providing fluid to inlet supplyline 6. Alternatively, the supply supplying fluid to the inlet supplyline 6 may be different than the supply 7 in fluid communication withfluid chambers 57, 58. Furthermore, a vent or pressure relief valve (notshown) may be present within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the hydraulic chamber 16 from an inlet supply line 6 andoptionally through an inlet check valve to pressurize the hydraulicchamber 16 and bias the piston 3 outward from the housing 2 in additionto the spring force from piston spring 4, to bias a span of the closedloop chain similar to FIG. 1 a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the hydraulic chamber 16 from an inletsupply line 6 and optionally through an inlet check valve to pressurizethe hydraulic chamber 16 and bias the piston 3 outward from the housing2 in addition to the spring force from piston spring 4, to bias a spanof the closed loop chain. As the chain wears, the piston 3 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. As a greater amount of fluid is required to add thespring force in biasing the piston 3 outwards from the housing 2, someof the fluid supplied to the hydraulic chamber 16 leaks to the fluidchambers 57, 58 between the moveable sleeve 163 and bore 2 a of thehousing. Since a top surface 161 of the bore flange 160 has a greaterarea A1 than the area A2 of the bottom surface 162 of the bore flange160, chamber 58 requires less fluid pressure to move the moveable sleeve163 outwards from the housing similar to FIG. 1b than chamber 57. Itshould be noted that the movable sleeve 163 is moved outwards mostly byoil from supply 7 and not the oil from hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 3 inwards towards thehousing 2 from the piston position shown in FIG. 1c (indicated by dashedlines). The inward force and motion of the piston 3 is resisted by thefluid in fluid chamber 58 since the check valve 53 in supply line 55,blocks fluid from exiting the fluid chamber 58, essentially pressurizingthe chamber 58. Furthermore, with the area A1 of the top surface 161 ofbore flange 160 being greater than the area A2 of the bottom surface 162of the bore flange 160, the pressurization of the fluid chamber 58causes the inner flange 164 of the moveable sleeve 163 to be “pumped” upor move outwards from the housing 2 and exert an outward force on thepiston 3 through the piston spring 4, opposing the inward force. Oncethe high load is removed from the piston 3, essentially depressurizingthe chamber 58, supply 7 supplies fluid through the check valve 53 andsupplies fluid to the fluid chamber 58 to fill the fluid chamber 58 andcompensate for the movement of the sleeve 163 relative to the piston 3and to maintain the position of the sleeve 163 relative to the piston 3.

Movement of the moveable sleeve 163 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

It should be noted that when fluid chamber 58 is depressurizing, fluidchamber 57 is pressurizing. The filling of fluid chamber 58 with fluidfrom supply 7 moves the moveable sleeve 163. The movement of themoveable sleeve 163 beyond or greater than the travel necessary tomaintain the position of the piston 3 relative to the chain is resistedby the fluid in fluid chamber 57 since the check valve 54, in supplyline 56 block fluid from exiting the fluid chamber 57, essentiallypressurizing the chamber 57. Once the load is removed from the sleeve,the fluid chamber 57 depressurizes and supply 7 supplies fluid throughthe check valve 54 and supplies fluid to the fluid chamber 57 to fillthe chamber 57 and compensates for movement of the sleeve 163 relativeto the piston 3 and maintains the position of the sleeve 163 relative tothe piston regardless of other forces acting on sleeve.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 163 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by the chamber 16, andfluid chambers 57, 58 of the tensioner and substantially prevents inwardmovement of piston 3 and the moveable sleeve 163 towards the housing 2when the chain span is under load.

FIG. 6 shows a passive tensioner system using internal pressure areasand flange pressures to move a moveable sleeve received by a piston.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. Received within the bore 2 a of the housing 2 is amoveable sleeve 80. The moveable sleeve 80 has a first opening 89 adefined by a top inner diameter portion 89 and a top surface 81 ofcentral flange 82 and a second opening 96 a defined by a bottom innerdiameter portion 96 and a bottom surface 83 of central inner flange 82.A through hole 97 of the central inner flange 82 connects the firstopening 89 a to the second opening 96 a of the moveable sleeve 80. A topsurface 98 of the moveable sleeve 80 is exposed to atmospheric pressureof the engine.

Received within the first opening 89 a of the moveable sleeve 80,defined by the top inner diameter portion 89 and the top surface 81 ofthe central inner flange 82 is a hollow piston 3. Within the hollowpiston 3 is a piston spring 4 biasing the piston 3 outwards from thehousing 2. The piston spring 4 has a first end 4 a in contact with theinner portion 3 a of the hollow piston 3 and a second end 4 b in contactwith a top surface 81 of the central inner flange 82 of the moveablesleeve 80.

Received within the second opening 96 a of the moveable sleeve 80,defined by the bottom inner diameter portion 96 and the bottom surface83 of the central inner flange 82 is a sleeve spring 5. The first end 5a of the sleeve spring 5 is in contact with a bottom surface 83 of thecentral flange 82 of the moveable sleeve 80 and the second end 5 b ofthe sleeve spring 5 is in contact with a bottom 2 c of the bore 2 a. Thesleeve spring 5 provides a bias force to reduce the control forcerequired to keep the moveable sleeve 80 in the desired position relativeto the piston 3. A pressure chamber 16 is formed the top inner diameterportion 89 of the sleeve 80, the bottom inner diameter portion 96 of thesleeve 80, the bore 2 a of the housing, and the interior 3 a of thepiston. The through hole 97 is present in the central inner flange 81and allows fluid from the inlet supply line 6 to flow from the secondopening 96 a to the first opening 89 a.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. The supply 7 providing fluid to the fluid chambers94, 95 may be the same as the supply providing fluid to inlet supplyline 6. Alternatively, the supply supplying fluid to the inlet supplyline 6 may be different than the supply 7 in fluid communication withfluid chambers 94, 95. Furthermore, a vent or pressure relief valve (notshown) may be present within the hollow piston 3.

The moveable sleeve 80 has an outer circumferential flange 84 which isapproximately equal to the width of the second diameter portion D2, butallowing the flange 84 to slide within the second diameter portion D2 ofthe bore 2 a and to form a first fluid chamber 95 and a second fluidchamber 94. The first fluid chamber 95 is connected to a supply 7through line 93, which preferably has a check valve 92 and the secondfluid chamber 94 is connected to a supply 7 through line 91, which alsopreferably has a check valve 90. The check valves 92, 90 prevent anyfluid in the fluid chambers 95, 94 from entering back into supply 7.Supply 7 provides fluid to the fluid chambers 94, 95 as necessary tomake up for leakage. The outer diameter of the moveable sleeve 80 belowthe outer circumferential flange 84 is received by a first diameterportion D1 of the bore 2 a, The second diameter portion D2 is greaterthan the first diameter portion D1.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the hydraulic chamber 16 from an inlet supply line 6 andoptionally through an inlet check valve to pressurize the hydraulicchamber 16 and bias the piston 3 outward from the housing 2 in additionto the spring force from piston spring 4, to bias a span of the closedloop chain similar to FIG. 1 a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the hydraulic chamber 16 from an inletsupply line 6 and optionally through an inlet check valve to pressurizethe hydraulic chamber 16 and bias the piston 3 outward from the housing2 in addition to the spring force from piston spring 4, to bias a spanof the closed loop chain. As the chain wears, the piston 3 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. As a greater amount of fluid is required to add thespring force in biasing the piston 3 outwards from the housing 2, someof the fluid supplied to the hydraulic chamber 16 leaks to the fluidchambers 94, 95 between the moveable sleeve 80 and bore 2 a of thehousing and the fluid pressure in chamber 16 on a bottom surface 99 ofthe sleeve 80 and on the bottom surface 83 of the central inner flange82 moves the sleeve 80 outwards from the housing similar to FIG. 1a . Itshould be noted that the movable sleeve is moved outwards mostly by oilfrom supply and not the oil from hydraulic chamber 16.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 3 inwards towards thehousing 2 from the piston position shown in FIG. 1c (indicated by dashedlines). The inward force and motion of the piston is resisted by thefluid in fluid chamber 94 since the check valve 90 in supply line 91blocks fluid from exiting the fluid chamber 94, essentially pressurizingthe chamber 94. The pressurization of fluid chamber 94 in addition tothe pressure on the bottom surface 99 on moveable sleeve 80 causes thecentral inner flange 82 of the moveable sleeve 80 to exert an outwardforce on the piston 3 through the piston spring 4, opposing the inwardforce. Once the high load is removed from the piston 3, essentiallydepressurizing the chamber 94, supply 7 supplies fluid through the checkvalve 10 and supplies fluid to the fluid chamber 94 to fill the fluidchamber 94 and compensate for the movement of the sleeve 80 relative tothe piston 3 and to maintain the position of the sleeve 80 relative tothe piston 3.

Movement of the moveable sleeve 80 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

It should be noted that when fluid chamber 94 is depressurizing, fluidchamber 95 is pressurizing. The filling of fluid chamber 94 with fluidfrom supply 7 moves the moveable sleeve 80. The movement of the moveablesleeve beyond or greater than the travel necessary to maintain theposition of the piston 3 relative to the chain is resisted by the fluidin fluid chamber 95 since the check valve 92, in supply line 93 blocksfluid from exiting the fluid chamber 95, essentially pressurizing thechamber 95. Once the load is removed from the sleeve 80, the chamber 95depressurizes and supply 7 supplies fluid through the check valve 92 andsupplies fluid to the fluid chamber 95 to fill the chamber 95 andcompensates for movement of the sleeve 80 relative to the piston 3 andmaintains the position of the sleeve 80 relative to the pistonregardless of other forces acting on sleeve.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 80 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by the pressure chamber16 and fluid chambers 94, 95 of the tensioner and substantially preventsinward movement of piston 3 and the moveable sleeve 80 towards thehousing 2 when the chain span is under load.

FIG. 7 shows a tensioner for a passive tensioner system.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with a firstdiameter portion D1 and a second diameter portion D2, with the seconddiameter portion D2 being larger than the first diameter portion D1. Abore flange 52 separates a second diameter portion D2 of the bore 2 athat receives the piston 3 and another second diameter portion D2 of thebore that receives an outer circumferential flange 20 of a moveablesleeve 18.

Received within the bore 2 a of the housing is a moveable sleeve 18. Themoveable sleeve 18 is hollow and forms a pressure chamber 16 with thebore 2 a of the housing 2, the inner diameter portion 17 of the hollowmoveable sleeve 18 and the interior of the piston 3. A sleeve spring 5is present within the bore 2 a and is received within the inner diameterportion 17 of the moveable sleeve 18, with a first end 5 a of the spring5 in contact with a bottom surface 24 of the inner flange 22 of themoveable sleeve 18 and second end 5 b of the spring 5 in contact withthe bottom 2 c of the bore 2 a. The sleeve spring 5 provides a biasforce to reduce the control force required to keep the moveable sleeve18 in the desired position relative to the piston 3.

The moveable sleeve 18 has an outer circumferential flange 20 with a topsurface 29 and a bottom surface 27. The outer circumferential flange 20separates a second diameter portion D2 of the housing 2 into first andsecond fluid chambers 58, 57. A first fluid chamber 58 is formed betweena top surface 29 of the outer circumferential flange 20 and the bottomsurface 51 of the bore flange 52 and a second fluid chamber 57 betweenthe bottom surface 27 of the outer circumferential flange 20 and anotherwall 73 of the second diameter portion D2.

The first fluid chamber 58 is connected to a supply 7 through line 101and a control valve 108. The second fluid chamber 57 is connected to asupply 7 through line 100 and control valve 108. Supply 7 supplies fluidto the fluid chambers 57, 58 to make up for leakage from the chambersonly. The control valve, 108, preferably a spool valve, includes a spool109 with at least two cylindrical lands 109 a, 109 b slidably receivedwithin a bore 106. The bore 106 may be in the tensioner housing 2 orlocated remotely from the tensioner housing in the engine. One end ofthe spool is in contact with a spring 110 that biases the spool in afirst direction.

At least a portion of the moveable sleeve 18 forward of the outercircumferential flange 20 is slidably received within the hollow piston3. Also present within the hollow piston 3 is a piston spring 4 biasingthe piston 3 outwards from the housing 2. The piston spring 4 has afirst end 4 a in contact with the inner portion 3 a of the hollow piston3 and a second end 4 b in contact with a top surface 26 of the innerflange 22 of the moveable sleeve 18. A through hole 47 is present in theinner flange 22 allowing fluid from the inlet supply line 6 to interior3 a of the piston and the top surface 26 of the inner flange 22 of themoveable sleeve 18.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. The supply 7 providing fluid to the fluid chambers57, 58 may the same as the supply providing fluid to inlet supply line6. Alternatively, the supply supplying fluid to the inlet supply line 6may be different than the supply 7 in fluid communication with fluidchambers 57, 58. Furthermore, a vent or pressure relief valve (notshown) may be present within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the hydraulic chamber 16 from an inlet supply line 6 andoptionally through an inlet check valve to pressurize the hydraulicchamber 16 and bias the piston 3 outward from the housing 2 in additionto the spring force from piston spring 4, to bias a span of the closedloop chain similar to FIG. 1 a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the hydraulic chamber 16 from an inletsupply line 6 and optionally through an inlet check valve to pressurizethe hydraulic chamber 16 and bias the piston 3 outward from the housing2 in addition to the spring force from piston spring 4, to bias a spanof the closed loop chain. As the chain wears, the piston 3 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. As a greater amount of fluid is required to add thespring force in biasing the piston 3 outwards from the housing 2, someof the fluid supplied to the hydraulic chamber 16 leaks to the fluidchambers 57, 58 between the moveable sleeve 18 and the bore 2 a of thehousing and moves the moveable sleeve 18 outwards from the housingsimilar to FIG. 1 b.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 3 inwards towards thehousing from the piston position shown in FIG. 1c (indicated by dashedlines). The inward force and motion of the piston 3 is resisted by thefluid in fluid chamber 57, since the spring force from spring 110 onspool valve 108 places land 109 a in a position relative to line 100 toblock fluid from exiting fluid chamber 57, essentially pressurizing thechamber 57. The pressurization of the fluid chamber 57 causes thecentral inner flange 22 of the moveable sleeve 40 to exert an outwardforce on the piston 3 through the piston spring 4, opposing the inwardforce. Once the high load is removed from the piston 3, essentiallydepressurizing the chamber 57, supply 7 supplies fluid through the spoolvalve 108 to fluid chamber 57 and compensates for movement of the sleeve40 relative to the piston 3 and to maintain the position of the sleeve40 relative to the piston 3.

Movement of the moveable sleeve 18 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

It should be noted that when fluid chamber 57 is depressurizing, fluidchamber 58 is pressurizing. The filling of fluid chamber 57 with fluidfrom supply 7 moves the moveable sleeve 18. The movement of the moveablesleeve 18 beyond or greater than the travel necessary to maintain theposition of the piston 3 relative to the chain is resisted by the fluidin fluid chamber 58 since the spool valve 108, blocks fluid from exitingthe fluid chamber 58, essentially pressurizing the chamber 58. Once theload is removed from the sleeve, the chamber 58 depressurizes and supply7 supplies fluid through the spool 108 and supplies fluid to the fluidchamber 58 to fill the chamber 58 and compensates for movement of thesleeve 18 relative to the piston 3 and maintains the position of thesleeve 18 relative to the piston regardless of other forces acting onsleeve.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 18 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by the chamber 16, andpressure chambers 57, 58 of the tensioner and substantially preventsinward movement of piston 3 and the moveable sleeve 40 towards thehousing 2 when the chain span is under load.

FIG. 8 is an alternate embodiment of FIG. 7 in which the control valve108 is in fluid communication with an accumulator 114. The accumulator114 is also in fluid communication with the pressure chamber 16 formedby the bore 2 a of the housing 2, the inner diameter portion 17 of thehollow moveable sleeve 18, and the interior 3 a of the piston 3 througha check valve 125. The accumulator 114 stores or accumulates fluid fromthe pressure chamber 16 to supply to fluid chambers 57, 58 in case ofleakage.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with a firstdiameter portion D1 and a second diameter portion D2, with the seconddiameter portion D2 being larger than the first diameter portion D1. Abore flange 52 separates a second diameter portion D2 of the bore 2 athat receives the piston 3 and another second diameter portion D2 of thebore that receives an outer circumferential flange 20 of a moveablesleeve 18.

Received within the bore 2 a of the housing is a moveable sleeve 18. Themoveable sleeve 18 is hollow and forms a pressure chamber 16 with thebore 2 a of the housing 2, the interior of the piston 3 and the innerdiameter portion 17 of the hollow moveable sleeve 18. A sleeve spring 5is present within the bore 2 a and is received within the inner diameterportion 17 of the moveable sleeve 18, with a first end 5 a of the spring5 in contact with a bottom surface 24 of the inner flange 22 of themoveable sleeve 18 and second end 5 b of the spring 5 in contact withthe bottom 2 c of the bore 2 a. The sleeve spring 5 provides a biasforce to reduce the control force required to keep the moveable sleeve18 in the desired position relative to the piston 3.

The moveable sleeve 18 has an outer circumferential flange 20 with a topsurface 29 and a bottom surface 27. The outer circumferential flange 20separates a second diameter portion D2 of the housing 2 into first andsecond fluid chambers 58, 57. A first fluid chamber 58 is formed betweena top surface 29 of the outer circumferential flange 20 and the bottomsurface 51 of the bore flange 52 and a second fluid chamber 57 betweenthe bottom surface 27 of the outer circumferential flange 20 and anotherwall 73 of the second diameter portion D2.

The first fluid chamber 58 is connected to accumulator 114 through line101, control valve 108 and line 112. The second fluid chamber 57 isconnected to accumulator 114 through line 100, control valve 108 andline 112. The accumulator 114 supplies fluid to chambers 57, 58 for makeup purposes due to leakage only. The control valve, 108, preferably aspool valve, includes a spool 109 with at least two cylindrical lands109 a, 109 b slidably received within a bore 106. The bore 106 may be inthe tensioner housing 2 or located remotely from the tensioner housingin the engine. One end of the spool is in contact with a spring 110 thatbiases the spool valve in a first direction.

At least a portion of the moveable sleeve 18 forward of the outercircumferential flange 20 is slidably received within the hollow piston3. Also present within the hollow piston 3 is a piston spring 4 biasingthe piston 3 outwards from the housing 2. The piston spring 4 has afirst end 4 a in contact with the inner portion 3 a of the hollow piston3 and a second end 4 b in contact with a top surface 26 of the innerflange 22 of the moveable sleeve 18. A through hole 47 is present in theinner flange 22 allowing fluid from the inlet supply line 6 to theinterior 3 a of the piston and the top surface 26 of the inner flange 22of the moveable sleeve 18.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. Furthermore, a vent or pressure relief valve (notshown) may be present within the hollow piston 3.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the hydraulic chamber 16 from an inlet supply line 6 andoptionally through an inlet check valve to pressurize the hydraulicchamber 16 and bias the piston 3 outward from the housing 2 in additionto the spring force from piston spring 4, to bias a span of the closedloop chain similar to FIG. 1 a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the hydraulic chamber 16 from an inletsupply line 6 and optionally through an inlet check valve to pressurizethe hydraulic chamber 16 and bias the piston 3 outward from the housing2 in addition to the spring force from piston spring 4, to bias a spanof the closed loop chain. As the chain wears, the piston 3 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. As a greater amount of fluid is required to add thespring force in biasing the piston 3 outwards from the housing 2, someof the fluid supplied to the hydraulic chamber 16 leaks to the fluidchambers 57, 58 between the moveable sleeve 18 and the bore 2 a of thehousing and moves the moveable sleeve 18 outwards from the housingsimilar to FIG. 1 b.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 3 inwards towards thehousing from the piston position shown in FIG. 1c (indicated by dashedlines). The inward force and motion of the piston is resisted by thefluid in fluid chamber 57, since the spring force from spring 110 onspool valve 108 places land 109 a in a position relative to line 100 toblock fluid from exiting fluid chamber 57, essentially pressurizing thechamber 57. The pressurization of the fluid chamber 57 causes thecentral inner flange 22 of the moveable sleeve 40 to exert an outwardforce on the piston 3 through the piston spring 4, opposing the inwardforce. Once the high load is removed from the piston 3, essentiallydepressurizing the chamber 57, accumulator 114 supplies fluid throughthe spool valve 108 to fluid chamber 57 to fill the fluid chamber 57 andcompensate for the movement of the sleeve 40 relative to the piston 3.

Movement of the moveable sleeve 40 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

It should be noted that when fluid chamber 57 is depressurizing, fluidchamber 58 is pressurizing. The filling of fluid chamber 57 with fluidfrom supply 7 moves the moveable sleeve 40. The movement of the moveablesleeve 40 beyond or greater than the travel necessary to maintain theposition of the piston 3 relative to the chain is resisted by fluid influid chamber 58 since spool valve 108 blocks fluid from exiting thefluid chamber 58, essentially pressurizing the chamber 57. Once the loadis removed from the piston 3, fluid chamber 58 depressurizes and fluidchamber 57 pressurizes.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 40 or any other place within the tensioner as necessary.

Hydraulic stiffness of the tensioner is created by the chamber 16, andpressure chambers 57, 58 of the tensioner and substantially preventsinward movement of piston 3 and the moveable sleeve 40 towards thehousing 2 when the chain span is under load.

FIG. 9 shows an active tensioner control system.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with a firstdiameter portion D1 and a second diameter portion D2, with the seconddiameter portion D2 being larger than the first diameter portion D1. Abore flange 52 separates a second diameter portion D2 of the bore 2 athat receives the piston 3 and another second diameter portion D2 of thebore that receives an outer circumferential flange 20 of the moveablesleeve 18 through a check valve 125.

Received within the bore 2 a of the housing 2 is a moveable sleeve 18.The moveable sleeve 18 is hollow and forms a pressure chamber 16 withthe bore 2 a of the housing 2, the interior 3 a of the piston 3 and theinner diameter portion 17 of the hollow moveable sleeve 18. A sleevespring 5 is present within the bore 2 a and is received within the innerdiameter portion 17 of the moveable sleeve 18, with a first end 5 a ofthe spring 5 in contact with a bottom surface 24 of the inner flange 22of the moveable sleeve 18 and second end 5 b of the spring 5 in contactwith the bottom 2 c of the bore 2 a. The sleeve spring 5 provides a biasforce to reduce the control force required to keep the moveable sleeve18 in the desired position relative to the piston 3.

The moveable sleeve 18 has an outer circumferential flange 20 with a topsurface 29 and a bottom surface 27. The outer circumferential flange 20separates a second diameter portion D2 of the housing 2 into first andsecond fluid chambers 58, 57. A first fluid chamber 58 is formed betweena top surface 29 of the outer circumferential flange 20 and the bottomsurface 51 of the bore flange 50 and a second fluid chamber 57 betweenthe bottom surface 27 of the outer circumferential flange 20 and anotherwall 73 of the second diameter portion D2.

The first fluid chamber 58 is in fluid communication with an accumulator114 through line 101, a control valve 108, and line 112. The secondfluid chamber 57 is in fluid communication with an accumulator 114through line 100, a control valve 108 and line 112. The accumulator 114is also preferably in fluid communication with the pressure chamber 16formed by the bore 2 a of the housing 2 and the inner diameter portion17 of the hollow moveable sleeve 18.

The control valve, 108, preferably a spool valve, includes a spool 109with at least two cylindrical lands 109 a, 109 b slidably receivedwithin a bore 106 that can block or allow flow from the accumulator 114to the fluid chambers 57, 58. The bore 106 may be in the tensionerhousing 2 or located remotely from the tensioner housing in the engine.One end of the control valve 108 is in contact with an actuator 116. Theactuator 116 is a position setting actuator or linear actuator in whichthe actuator sets a specific position of the control valve 108. In analternate embodiment the actuator 116 may also be a force actuator inwhich a force is present on one side of the control valve. It should benoted that if the actuator 116 is a force actuator a spring would bepresent on the opposite side of control valve influenced by the actuator116.

The actuator is controlled by a controller 118 which receives a setpoint input 122 from a set point algorithm or map 124. The controller118 also receives position feedback 120 of the moveable sleeve 18 of thetensioner via a sensor (not shown). The set point algorithm or map 124receives input from different engine parameters 126, such as, but notlimited to cam timing, engine speed, throttle, temperature, age, andtensioner position.

At least a portion of the moveable sleeve 18 forward of the outercircumferential flange 20 is slidably received within the hollow piston3. Also present within the hollow piston 3 is a piston spring 4 biasingthe piston 3 outwards from the housing 2. The piston spring 4 has afirst end 4 a in contact with the inner portion 3 a of the hollow piston3 and a second end 4 b in contact with a top surface 26 of the innerflange 22 of the moveable sleeve 18. A through hole 47 is present in theinner flange 22 allowing fluid from the inlet supply line 6 to the innerportion 3 a of the piston 3.

At the bottom of the bore 2 a an inlet check valve may be present (notshown) as well as an inlet supply line 6 to provide oil pressure to thepressure chamber 16. Furthermore, a vent or pressure relief valve (notshown) may be present within the hollow piston 3.

During operation, fluid is supplied to the hydraulic chamber 16 from aninlet supply line 6 and optionally through an inlet check valve topressurize the hydraulic chamber 16 and the chamber 9 formed within theinner portion 3 a of the piston and bias the piston outward from thehousing 2 with the spring force from piston spring 4 to bias a span ofthe closed loop chain.

A sensor (not shown) provides position feedback 120 of the moveablesleeve 18 to the controller 118. The controller 118 compares theposition feedback of the moveable sleeve to the set point 122 from theset point algorithm or map 124 based on different engine parameters 126.

If the position of the moveable sleeve 18 is equivalent to the set point122, then the control valve 108 is not moved or actuated and the lands109 a, 109 b, blocks the flow of fluid from the accumulator 114 to thefluid chambers 57, 58. Furthermore since no fluid is being added orremoved from the fluid chambers 57, 58, the position of the moveablesleeve 18 relative to the piston 3 and bore 2 a of the housing ismaintained.

If the position of the moveable sleeve 18 is not equivalent to the setpoint 122, then the control valve 108 is actuated by the actuator 116 toa position in which fluid flows from the accumulator 114 to the fluidchambers 57, 58 to move the moveable sleeve 18 relative to the piston 3and the bore 2 a of the housing. The movement of the moveable sleeve 18moves the location of the second end 4 b of the piston spring 4 which isin contact with a top surface 26 of the inner flange 22 of the moveablesleeve 18, biasing the piston 3 outwards from the housing 2 and intocontact with a span of a chain or belt (not shown). With the second end4 b of the piston spring 4 biasing the piston 3 outwards from thehousing 2 being moveable, the spring force acting on the piston 3 isvariable and the piston 3 continually tensions the chain, even when thechain becomes worn and stretched.

Movement of the moveable sleeve 18 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

Hydraulic stiffness of tensioner created by the chamber 16, and fluidchambers 57 and 58 of the tensioner and substantially prevents inwardmovement of piston 3 and the moveable sleeve 18 towards the housing 2when the chain span is under load.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 40 or any other place within the tensioner as necessary.

FIG. 10 an active control tensioner system.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. Received within the bore 2 a of the housing 2 is amoveable sleeve 80. The moveable sleeve 80 has a first opening 89 adefined by a top inner diameter portion 89 and a top surface 82 ofcentral inner flange 81 and a second opening 96 a defined by a bottominner diameter portion 96 and a bottom surface 83 of central innerflange 81. A through hole 97 of the central inner flange 81 connects thefirst opening 89 a to the second opening 96 a of the moveable sleeve 80.The moveable sleeve 80 also has a top surface 98.

Received within the first opening 89 a of the moveable sleeve 80,defined by the top inner diameter portion 89 and the top surface 82 ofthe central inner flange 81 is a hollow piston 3. Within the hollowpiston 3 is a piston spring 4 biasing the piston 3 outwards from thehousing 2. The piston spring 4 has a first end 4 a in contact with theinner portion 3 a of the hollow piston 3 and a second end 4 b in contactwith a top surface 82 of the central inner flange 81 of the moveablesleeve 80.

Received within the second opening of the moveable sleeve 80, defined bythe bottom inner surface 96 and the bottom surface 83 of the centralinner flange 81 is a sleeve spring 5. The first end 5 a of the sleevespring 5 is in contact with a bottom surface 83 of the central innerflange 81 of the moveable sleeve 80 and the second end 5 b of the sleevespring 5 is in contact with a bottom of the bore 2 a. The sleeve spring5 provides a bias force to reduce the control force required to keep themoveable sleeve 80 in the desired position relative to piston 3. Apressure chamber 16 is formed between first and second openings 89, 96of the moveable sleeve 80, the bore 2 a and the interior 3 a of thepiston 3. The through hole 97 is present in the central inner flange 81allows fluid from the inlet supply line 6 to interior 3 a of the pistonand the top surface 82 of the central inner flange 81 of the moveablesleeve 80.

At the bottom 2 c of the bore 2 a an inlet check valve may be present(not shown) as well as an inlet supply line 6 to provide oil pressure tothe pressure chamber 16. Furthermore, a vent or pressure relief valve(not shown) may be present within the hollow piston 3.

The moveable sleeve 80 has an outer circumferential flange 84 which isapproximately equal to the width of the second diameter portion D2, butallowing the flange 84 to slide within the second diameter portion D2 ofthe bore 2 a and to form a first fluid chamber 95 and a second fluidchamber 94. The first fluid chamber 95 is connected to an accumulator114 through line 101, a control valve 108 and line 112. The second fluidchamber 94 is connected to the accumulator 114 through line 100, thecontrol valve 108 and line 112. The accumulator 114 is also preferablyin fluid communication with the pressure chamber 16 formed by the bore 2a of the housing 2 and the bottom inner surface 96 a of the secondopening 96 of the moveable sleeve 80 through a check valve 125.

The control valve, 108, preferably a spool valve, includes a spool 109with at least two cylindrical lands 109 a, 109 b slidably receivedwithin a bore 106 that can block or allow flow from the accumulator 114to the fluid chambers 94, 95. The bore 106 may be in the tensionerhousing 2 or located remotely from the tensioner housing in the engine.One end of the control valve 108 is in contact with an actuator 116. Inthis embodiment, the actuator 116 is a position setting actuator orlinear actuator in which the actuator sets a specific position of thecontrol valve. In an alternate embodiment the actuator 116 may also be aforce actuator in which a force is present on one side of the controlvalve. It should be noted that if the actuator 116 is a force actuator aspring would be present on the opposite side of control valve influencedby the actuator 116.

The actuator position is controlled by a controller 118 which receives aset point input 122 from a set point algorithm or map 124. Thecontroller 118 also receives position feedback 120 of the moveablesleeve 80 of the tensioner via a sensor (not shown). The set pointalgorithm or map 124 receives input from different engine parameters126, such as, but not limited to cam timing, engine speed, throttle,temperature, age, and tensioner position.

During operation, fluid is supplied to the hydraulic chamber 16 from aninlet supply line 6 and optionally through an inlet check valve topressurize the hydraulic chamber 16 and bias the piston outward from thehousing 2 with the spring force from piston spring 4 to bias a span ofthe closed loop chain.

A sensor (not shown) provides position feedback 120 of the moveablesleeve 80 to the controller 118. The controller 118 compares theposition feedback of the moveable sleeve to the set point 122 from theset point algorithm or map 124 based on different engine parameters 126.

If the position of the moveable sleeve 80 is equivalent to the set point122, then the control valve 108 is not moved or actuated and the lands109 a, 109 b, blocks the flow of fluid from the accumulator 114 to thefluid chambers 94, 95. Furthermore since no fluid is being added orremoved from the fluid chambers 94, 95, the position of the moveablesleeve 80 relative to the piston 3 and bore 2 a of the housing ismaintained.

If the position of the moveable sleeve 80 is not equivalent to the setpoint 122, then the control valve 108 is actuated by the actuator to aposition in which fluid flows from the accumulator 114 to the fluidchambers 94, 95 to move the moveable sleeve 80 relative to the piston 3and the bore 2 a of the housing. The movement of the moveable sleeve 80moves the location of the second end 4 b of the piston spring 4 which isin contact with a top surface 81 of the central inner flange 81 of themoveable sleeve 80, biasing the piston 3 outwards from the housing 2 andinto contact with a span of a chain or belt (not shown). With the secondend 4 b of the piston spring 4 biasing the piston 3 outwards from thehousing 2 being moveable, the spring force acting on the piston 3 isvariable and the piston 3 continually tensions the chain, even when thechain becomes worn and stretched.

Movement of the moveable sleeve 80 moves the second end 4 b of thepiston spring 4 biasing the piston 3 outwards from the housing 2, andtherefore the spring force acting on the piston 3 is variable and thepiston 3 continually tensions the chain, even when the chain becomesworn and stretched.

Hydraulic stiffness of tensioner created by the chamber 16, and fluidchambers 94 and 95 of the tensioner and substantially prevents inwardmovement of piston 3 and the moveable sleeve 80 towards the housing 2when the chain span is under load.

Seals (not shown) may be present between the bore 2 a and the moveablesleeve 80 or any other place within the tensioner as necessary.

FIGS. 11a-11c show the tensioner tensioning under various chainconditions; FIG. 11a is tensioning a new chain; FIG. 11b is tensioning aworn chain without high loads; FIG. 11c is tensioning a worn chain underhigh load.

The tensioner is comprised of a housing 202 having an axially extendingpiston bore 202 a. Received within the bore 202 a is a hollow sleeve230. The hollow sleeve 230 is fixed to the bottom 202 c of the bore 202a but may be allowed to move laterally within the bore 202 a. Receivedwithin the hollow sleeve 230 and the bore 202 a is a sleeve spring 205,an internal piston 232 and an external piston spring 204. The internalpiston 232 has a body with a first end 232 a and a second end 232 b.Also received within the bore 202 a of the housing 202 is an externalpiston 203 with a body having an open end with a bottom surface 203 b, aclosed end and a hollow interior 203 a with an inner diameter.

The sleeve spring 205 has a first end 205 a in contact with the secondend 232 b of the internal piston 232 and a second end 205 b in contactwith the bottom 202 c of the bore 202 a or a flange at the bottom of thehollow sleeve 230 as shown in other embodiments. The sleeve spring 205provides a bias force to reduce the control force required to keep theinternal piston 232 in the desired position relative to the externalpiston 203. The stiffness of the external piston spring 204 is greaterthan the stiffness of the sleeve spring 205, since ideally the averagelength of the external piston spring 204 is unchanged as chain lengthincreases.

An internal piston pressure chamber 211 is formed between the interior230 a of the hollow sleeve 230, the second end 232 b of the internalpiston 232, the bottom 202 c of the bore 202 a, and the sleeve spring205.

An external piston pressure chamber 214 is formed between the bore 202a, an outer surface 230 b of the hollow sleeve 230, and a bottom surfaceor end 203 b of the external piston 203. The external piston pressurechamber 214 is in fluid communication with an oil pressure supply 207through a supply line 212 containing a check valve 210. The supply 207supplies fluid to the external piston pressure chamber 214 to make upfor any leakage that may occur. The check valve 210 prevents any fluidin the external piston pressure chamber 214 from entering back into thesupply 207. The external piston pressure chamber 214 may also be incommunication with a pressure relief valve 234.

At least a portion of the internal piston 232 is slidably receivedwithin the hollow piston 203. Also present within the hollow piston 203is an external piston spring 204 biasing the external piston 203outwards from the housing 202. The external piston spring 204 has afirst end 204 a in contact with the interior 203 a of the externalhollow piston 203 and a second end 204 b in contact with a first end 232a of the internal piston 232. The stiffness of the external pistonspring 204 is greater than the stiffness of the sleeve spring 205, sinceideally the average length of the external piston spring 204 isunchanged. The hollow sleeve 230 may also be received within the hollowpiston 203. It should be noted that a chamber 209 formed between theinterior 203 a of the hollow piston 203, the piston spring 204, theinternal piston 232 and the hollow sleeve 230 is preferably atatmosphere or atmospheric pressure. Any fluid in this chamber 209 isvented, for example through a vent 238 in the external piston 203.

At the bottom end of the bore 202 a an inlet check valve may be present(indicated by box 208) as well as an inlet supply line 206 to provideoil pressure to the internal pressure chamber 211. The supply 207providing fluid to the external piston pressure chamber 214 may be thesame as the supply providing fluid to inlet supply line 206.Alternatively, the supply supplying fluid to the inlet supply line 206may be different than the supply 207 in fluid communication withexternal piston pressure chamber 214.

Referring to FIG. 11a , when the tensioner is tensioning a new chain,during operation, fluid is supplied to the external piston pressurechamber 214 from supply 207 through a check valve 210 to pressurize theexternal piston pressure chamber 214 and bias the external piston 203outward from the housing 202 in addition to the spring force fromexternal piston spring 204, to bias a span of the closed loop chain.

Referring to FIG. 11b , when the tensioner is tensioning a worn chain,without high load, during operation, fluid is supplied to the externalpiston pressure chamber 214 from a supply 207 and through a check valve210 to pressurize the external piston pressure chamber 214 and bias theexternal piston 203 outward from the housing 202 in addition to thespring force from external piston spring 204, to bias a span of theclosed loop chain. As the chain wears, the external piston 203 has to bebiased further outwards from the housing 202 in order to adequatelytension the chain. The additional distance that the external piston 203needs to be biased outwards from the housing 202 is provided by movementof the internal piston 232, which also moves the second end 204 b of thespring 204 outwards from the housing as well.

Referring to FIG. 11c , when the tensioner is tensioning a worn chainduring high chain load, during operation, the high force pushes theexternal piston 203 inwards towards the housing 202 from the pistonposition shown in FIG. 11b (indicated by dashed lines). The inward forceand motion of the external piston 203 is resisted by the fluid in theexternal piston pressure chamber 214, since the check valve 210 insupply line 212 blocks and fluid from exiting the external pistonpressure chamber 214, essentially pressurizing the external pistonpressure chamber 214. The pressurization of the external piston pressurechamber 214 causes the inner piston 232 to exert an outward force on thepiston 203 through the external piston spring 204, opposing the inwardforce. Once the high load is removed from the piston 203, essentiallydepressurizing the external piston pressure chamber 214, supply 207supplies fluid through the check valve 210 and supplies fluid to theexternal piston pressure chamber 214 to fill the external pistonpressure chamber 214 and compensate for the movement of the internalpiston 232 relative to the external piston 203 and to maintain theposition of the internal piston 232 relative to the external piston 203.

Movement of the internal piston 232 moves the second end 204 b of theexternal piston spring 204 biasing the external piston 203 outwards fromthe housing 202, and therefore the spring force acting on the externalpiston 203 is variable and the external piston 203 continually tensionsthe chain, even when the chain becomes worn and stretched.

A partial seal or seal may be present between the internal piston 232and the hollow sleeve 232; between the hollow sleeve 230 and theexternal piston 203 and between external piston 203 and bore 202 a.

Hydraulic stiffness of the tensioner is created by pressure in theinternal piston pressure chamber 211 and external piston pressurechamber 214 of the tensioner and substantially prevents inward movementof external piston 203 and the internal piston 232 towards the housing202 when the chain span is under load.

Damping may be added to the tensioner by adjusting the leakage of theexternal piston pressure chamber 214 through the pressure relief valve234.

FIGS. 12a-12c shows a tensioner under various chain conditions; FIG. 12ais tensioning a new chain; FIG. 12b is tensioning a worn chain withouthigh loads; FIG. 12c is tensioning a worn chain under high load.

The tensioner is comprised of a housing 202 having an axially extendingpiston bore 202 a. Received within the bore 202 a is a hollow sleeve230. The hollow sleeve 230 is fixed to the bottom 202 c of the bore 202a but may be allowed to move laterally within the bore 202 a. Receivedwithin the hollow sleeve 230 and the bore 202 a is an internal piston242 with a body that has a first end 242 a, a second end 242 b andcircumferential flange 220 with a first (outward or top) surface 229 anda second (inner or bottom) surface 227 between the first end 242 a andthe second end 242 b of the internal piston 242. Also received withinthe bore 202 a is an internal piston spring 245 and an external pistonspring 204. At least a portion of the internal piston 242 is slidablyreceived within the external hollow piston 203. The external piston 203has a body having an open end with a bottom surface 203 b, a closed endand a hollow interior 203 a with an inner diameter.

The internal piston spring 245 has a first end 245 a in contact withbottom surface 227 of the circumferential flange 220 of the internalpiston 242 and a second end 245 b in contact with the bottom 202 c ofthe bore 202 a of a flange at the bottom of the hollow sleeve 230. Theinternal piston spring 245 provides a bias force to reduce the controlforce required to keep the internal piston 232 in the desired positionrelative to the external piston 203. The external piston spring 204 hasa first end 204 a in contact with an end 203 b of the hollow externalpiston 203 and a second end 204 b in contact with a top surface 229 ofthe circumferential flange 220 of the internal piston 232. The stiffnessof the external piston spring 204 is greater than the stiffness of theinternal piston spring 245, since ideally the average length of theexternal piston spring 204 is unchanged as chain length increases.

Alternatively, the external piston spring 204 may be placed between theinterior 203 a of the external piston and the top surface 242 a of theinternal piston 242 and the internal piston spring 245 placed betweenthe internal piston 242 and the bottom 202 c of the cylindrical bore 202a or a flange present on the hollow fixed sleeve 230.

An internal piston pressure chamber 246 is formed between the hollowsleeve 230, the bottom 202 c of the bore 202 a and the second end 242 bof the internal piston 242.

An external piston pressure chamber 247 is formed between the bore 202a, an outer surface 230 b of the hollow sleeve 230, a bottom surface 203b of the hollow external piston 203, and the internal piston 232. Theexternal piston pressure chamber 247 is in fluid communication with anoil pressure supply 207 through a supply line 232 containing a checkvalve 210. The supply 207 supplies fluid to the external piston pressurechamber 247 to make up for any leakage that may occur. The check valve210 prevents any fluid in the external piston pressure chamber 247 fromentering back into the supply 207. The external piston pressure chamber247 may also be in fluid communication with a pressure relief valve 234.

It should be noted that a chamber 209 formed between the interior 203 aof the external hollow piston 203 and the first end of the internalpiston 242 is preferably at atmosphere. Any fluid that may end uppresent within the chamber 209 may be vented through vent 238 of theexternal piston 203.

At the bottom of the bore 202 a an inlet check valve may be present(indicated by box 208) as well as an inlet supply line 206 to provideoil pressure to the internal piston pressure chamber 246. The supply 207providing fluid to the external piston pressure chamber 247 may be thesame as the supply providing fluid to inlet supply line 206.Alternatively, the supply supplying fluid to the inlet supply line 206may be different than the supply 207 in fluid communication withexternal piston pressure chamber 247.

When the tensioner is tensioning a new chain, for example as shown inFIG. 12a , during operation, fluid is supplied to the external pistonpressure chamber 247 from supply 207 through a check valve 210 topressurize the external piston pressure chamber 247 and bias theexternal piston 203 outward from the housing 202 in addition to thespring force from piston spring 204, to bias a span of the closed loopchain.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 12b , without high load, during operation, fluid is supplied to theexternal piston pressure chamber 247 from a supply 207 and through acheck valve 210 to pressurize the external piston pressure chamber 247and bias the external piston 203 outward from the housing 202 inaddition to the spring force from external piston spring 204, to bias aspan of the closed loop chain. As the chain wears, the external piston203 has to be biased further outwards from the housing 202 in order toadequately tension the chain. The additional distance that the externalpiston 203 needs to be biased outwards from the housing 202 is providedby movement of the internal piston 242, which also moves the second end204 b of the external piston spring 204 outwards from the housing 202 aswell.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 12c , during operation, the high forcepushes the external piston 203 inwards towards the housing 202 from thepiston position for example shown in FIG. 12b (indicated by dashedlines). The inward force and motion of the external piston 203 isresisted by the fluid in the external piston pressure chamber 247, sincethe check valve 210 in supply line 212 blocks fluid from exiting theexternal piston pressure chamber 247, essentially pressurizing theexternal piston pressure chamber 247. The pressurization of the externalpiston pressure chamber 247 causes the circumferential flange 220 of theinternal piston 242 to exert an outward force on the external piston 203through the external piston spring 204, opposing the inward force. Oncethe high load is removed from the external piston 203, essentiallydepressurizing the external piston pressure chamber 247, supply 207supplies fluid through the check valve 210 and supplies fluid to theexternal piston pressure chamber 247 to fill the external pistonpressure chamber 247 and compensate for the movement of the internalpiston 242 relative to the external piston 203 and to maintain theposition of the internal piston 242 relative to the external piston 203.

Movement of the internal piston 242 moves the second end 204 b of theexternal piston spring 204 biasing the external piston 203 outwards fromthe housing 202, and therefore the spring force acting on the externalpiston 203 is variable and the external piston 203 continually tensionsthe chain, even when the chain becomes worn and stretched.

A seal or partial seal may be present between the internal piston 242and the hollow sleeve 230; between the hollow sleeve 230 and theexternal piston 203 and between external piston 203 and bore 202 a.

Hydraulic stiffness of the tensioner is created by pressure in theinternal piston pressure chamber 246 and external piston pressurechamber 247 of the tensioner and substantially prevents inward movementof external piston 203 and the internal piston 242 towards the housing202 when the chain span is under load.

Damping may be added to the tensioner by adjusting the leakage of theexternal piston pressure chamber 247 through the pressure relief valve234.

FIGS. 13a-13c shows a tensioner tensioning under various chainconditions; FIG. 13a is tensioning a new chain; FIG. 13b is tensioning aworn chain without high loads; FIG. 13c is tensioning a worn chain underhigh load.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with first diameterportion D1 and a second diameter portion D2, with the second diameterportion D2 being larger than the first diameter portion D1.

Received within the piston bore 2 a is an internal piston 232 with afirst end 232 a and a second end 232 b. Received within the bore 2 a ofthe housing 2 a is an internal piston spring 245 with a first end 245 ain contact with the second end 232 b of the internal piston 232. Thesecond end 245 b of the internal piston spring 245 is in contact withthe bottom 2 c of the bore 2 a of the housing 2. The internal pistonspring 245 provides a bias force to reduce the control force required tokeep the internal piston 232 in the desired position relative to anexternal piston 203. Also received within the bore 202 a of the housing202 is an external piston 203 with a body having an open end with abottom surface 203 b, a closed end and a hollow interior 203 a with aninner diameter.

An internal piston pressure chamber 248 is formed between the interiorof the bore 2 a with first diameter portion D1, the bottom 2 c of thebore 2 a, the internal piston spring 245, and the second end 232 b ofthe internal piston 232.

An external piston pressure chamber 249 is formed between the interiorof the bore 2 a with second diameter portion D2, an outer surface of theinternal piston 232, and an end 203 b of the external piston 203. Theexternal piston pressure chamber 249 is in fluid communication with anoil pressure supply 207 through a supply line 212 containing a checkvalve 210. The supply 207 supplies fluid to the external piston pressurechamber 249 to make up for any leakage that may occur. The check valve210 prevents any fluid in the external piston pressure chamber 249 fromentering back into the supply 207. The external piston pressure chamber249 is also in communication with a pressure relief valve 234.

At least a portion of the internal piston 232 is slidably receivedwithin the external hollow piston 203. Also present within the externalhollow piston 203 is a piston spring 204 biasing the piston 203 outwardsfrom the housing 202. The piston spring 204 has a first end 204 a incontact with the interior 203 a of the hollow piston 203 and a secondend 204 b in contact with a first end 232 a of the internal piston 232.The piston spring 204 has a greater spring stiffness than the internalpiston spring 245. It should be noted that a chamber 209 formed betweenthe interior 203 a of the hollow piston 203, the piston spring 204, andthe internal piston 232 is preferably at atmosphere. Furthermore, a vent238 may be present within the external hollow piston 203.

At the bottom 2 c of the bore 2 a an inlet check valve may be present(indicated by box 208) as well as an inlet supply line 206 to provideoil pressure to the internal pressure chamber 248. The supply 207providing fluid to the external piston pressure chamber 249 may be thesame as the supply providing fluid to inlet supply line 206.Alternatively, the supply supplying fluid to the inlet supply line 206may be different than the supply 207 in fluid communication withexternal piston pressure chamber 249.

When the tensioner is tensioning a new chain, for example as shown inFIG. 13a , during operation, fluid is supplied to the external pistonpressure chamber 249 from supply 207 through a check valve 210 topressurize the external piston pressure chamber 249 and bias theexternal piston 203 outward from the housing 2 in addition to the springforce from the external piston spring 204, to bias a span of the closedloop chain.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 13b , without high load, during operation, fluid is supplied to theexternal piston pressure chamber 249 from supply 207 and through a checkvalve to pressurize the external piston pressure chamber 249 and biasthe external piston 203 outward from the housing 2 in addition to thespring force from the external piston spring 204, to bias a span of theclosed loop chain. As the chain wears, the external piston 203 has to bebiased further outwards from the housing 2 in order to adequatelytension the chain. The additional distance that the external piston 203needs to be biased outwards from the housing 2 is provided by movementof the internal piston 232, which also moves the second end 204 b of theexternal piston spring 204 outwards from the housing 2 as well.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 13c , during operation, the high forcepushes the external piston 203 inwards toward the housing 2 from thepiston position for example shown in FIG. 13b (indicated by dashedlines). The inward force and motion of the external piston 203 isresisted by the fluid in the external piston pressure chamber 249, sincethe check valve 210 in supply line 212 blocks fluid from exiting theexternal piston pressure chamber 249, essentially pressurizing theexternal piston pressure chamber 249. The pressurization of the externalpiston pressure chamber 249 causes the internal piston 232 to exert anoutward force on the external piston 203 through the external pistonspring 204, opposing the inward force. Once the high load is removedfrom the piston 203, essentially depressurizing the external pistonpressure chamber 249, supply 207 supplies fluid through the check valve210 and supplies fluid to the external piston pressure chamber 249 tofill the external piston pressure chamber 249 and compensate for themovement of the internal piston 232 relative to the external piston 203and to maintain the position of the internal piston 232 relative to theexternal piston 203.

Movement of the internal piston 232 moves the second end 204 b of theexternal piston spring 204 biasing the external piston 203 outwards fromthe housing 2, and therefore the spring force acting on the externalpiston 203 is variable and the external piston 203 continually tensionsthe chain, even when the chain becomes worn and stretched.

A seal or partial seal may be present between the internal piston 232and the external piston 203 and between external piston 203 and bore 202a.

Hydraulic stiffness of the tensioner is created by pressure in theinternal piston pressure chamber 245 and external piston pressurechamber 249 of the tensioner and substantially prevents inward movementof external piston 203 and the internal piston 232 towards the housing232 when the chain span is under load.

Damping may be added to the tensioner by adjusting the leakage of theexternal piston pressure chamber 249 through the pressure relief valve234.

While internal piston 232 is shown as being solid and one piece, itcould be two separate solid pistons, two separate hollow pistons, or acombination of the two. The two separate solid pistons, two separatehollow pistons, or a combination of solid and hollow pistons may bearranged to contact one another within the cylindrical bore 2 a, withone of the pistons slidably received within the first diameter portionD1 of the cylindrical bore 2 a and the other of the pistons slidablyreceived within the open end of external piston 203.

FIGS. 14a-14c shows a tensioner tensioning under various chainconditions; FIG. 14a is tensioning a new chain; FIG. 14b is tensioning aworn chain without high loads; FIG. 14c is tensioning a worn chain underhigh load.

The tensioner is comprised of a housing 202 having an axially extendingpiston bore 202 a. A hollow moveable sleeve 33 is received within thebore 202 a of the housing 202. The hollow moveable sleeve 33 has aninner flange 34 with a top surface 35 and a bottom surface 36. A throughhole 25 is present in the inner flange 34 to receive the shaft 272 ofthe piston 270.

Received within the hollow moveable sleeve 33 is a fixed hollow sleeve30. Also received within the hollow moveable sleeve 33 and the fixedhollow sleeve 30 is a portion of the external tensioner piston 270. Theexternal tensioner piston 270 includes a head 271 connected to a shaft272 having a bottom end or surface 272 a. The head 271 has a first ortop surface 271 a which contacts the arm 351 or chain/belt 350 and abottom surface 271 b.

A piston pressure chamber 274 is formed between end 272 a of the shaftof the external piston 270, the bottom 202 c of the bore 202 a, and/orthe inner diameter portion 38 of the fixed sleeve 30.

A piston spring 277 is present between the head 271 of the piston andthe moveable sleeve 33. A first end 277 a of the piston spring 277 is incontact with the bottom surface 271 b of the head 271 of the piston 270and the second end 277 b of the piston spring 277 is in contact with atop surface 35 of the inner flange 34 of the moveable sleeve 33.

A sleeve spring 278 is present between the bore 202 a of the housing 202and the moveable sleeve 33, with a first end 278 a of the sleeve springin contact with a bottom surface 39 of the moveable sleeve 33 and asecond end 278 b of the sleeve spring 278 in contact with the bottom 202c of the bore 202 a or a flange at the bottom of the fixed hollow sleeve230.

A sleeve pressure chamber 276 is formed between the bore 202 a, thesleeve spring 278, the fixed sleeve 30 and a bottom end surface 39 ofthe moveable sleeve 33. The sleeve pressure chamber 276 is in fluidcommunication with an oil pressure supply 207 through a supply line 212containing a check valve 210. The supply 207 supplies fluid to thesleeve pressure chamber 276 to make up for any leakage that may occur.The check valve 210 prevents any fluid in the sleeve pressure chamber276 from entering back into the supply 207.

The chamber 279 present between the fixed sleeve 30 and a bottom surface36 of an inner flange 24 of the moveable sleeve 33 is at atmosphere. Anyfluid that may be present in the chamber 279 may leak through theclearances present between the inner flange 24 and the shaft 272 of thepiston 270.

The stiffness of the piston spring 277 is greater than the stiffness ofthe sleeve spring 278, since ideally the average length of the pistonspring 277 is unchanging as the chain length increases.

When the tensioner is tensioning a new chain, for example as shown inFIG. 14a , during operation, fluid is supplied to the piston pressurechamber 274 from an inlet supply line 206 and optionally through aninlet check valve (not shown) to pressurize the piston pressure chamber274 and bias the piston 270 outward from the housing 202 in addition tothe spring force from piston spring 277, to bias a span of the closedloop chain.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 14b , without high load, during operation, fluid is supplied to thepiston pressure chamber 274 from an inlet supply line 206 and optionallythrough an inlet check valve to pressurize the piston pressure chamber274 and bias the piston 270 outwards from the housing 202 in addition tothe spring force from the piston spring 277, to bias a span of theclosed loop chain. As the chain wears, the piston 270 has to be biasedfurther outwards from the housing 202 in order to adequately tension thechain and the moveable sleeve 33 moves outwards.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 14c , during operation, the high forcepushes the piston 270 inwards toward the housing 2 from the pistonposition shown in FIG. 14b (indicated by the dashed lines). The inwardforce and the motion of the piston 270 is resisted by the fluid in thesleeve pressure chamber 276, since the check valve 210 in supply line212 blocks fluid from exiting the sleeve pressure chamber 276,essentially pressurizing the sleeve pressure chamber 276. Thepressurization of sleeve pressure chamber 276 causes inner flange 34 ofthe moveable sleeve 33 to exert an outward force on the piston 270through the piston spring 277, opposing the inward force. Once the highload is removed from the piston 270, essentially depressurizing thesleeve pressure chamber 276, supply 207 supplies fluid through the checkvalve 210 and supplies fluid to the fluid chamber sleeve pressurechamber 276 to fill the sleeve pressure chamber 276 and compensate forthe movement of the sleeve 33 relative to the piston 270 and to maintainthe position of the sleeve 33 relative to the piston 270.

Movement of the moveable sleeve 33 moves the second end 277 b of thepiston spring 277 biasing the piston 270 outwards from the housing 202,and therefore the spring force acting on the piston 270 is variable andthe piston 270 continually tensions the chain, even when the chainbecomes worn and stretched.

Hydraulic stiffness of the tensioner is created by piston pressurechamber 274 and sleeve pressure chamber 276 of the tensioner andsubstantially prevents inward movement of piston 270 and the moveablesleeve 33 towards the housing 202 when the chain span is under load.

FIG. 15 shows a tensioner using supply pressure to move a moveablesleeve 33 surrounding a piston 270. The difference between thisembodiment and the embodiments of FIG. 14a-14c is placement of thesleeve spring.

The tensioner is comprised of a housing 202 having an axially extendingpiston bore 202 a. A hollow moveable sleeve 33 is received within thebore 202 a of the housing 202. The hollow moveable sleeve 33 has aninner flange 34 with a top surface 35 and a bottom surface 36. A throughhole 25 is present in the inner flange 34 to receive the shaft 272 ofthe piston 270.

Received within the hollow moveable sleeve 33 is a fixed hollow sleeve30. Also received within the hollow moveable sleeve 33 and the fixedhollow sleeve 30 is a portion of the external tensioner 270. Theexternal tensioner piston 270 includes a head 271 connected to a shaft272 having a bottom end or surface 272 a. The head 271 has a first ortop surface 271 a which contacts the arm 351 or chain/belt 350 and abottom surface 271 b.

A piston pressure chamber 274 is formed between end 272 a of the shaftof the external piston 270, the bottom 202 c of the bore 202 a, and theinner diameter portion 38 of the fixed sleeve 30.

A piston spring 277 is present between the head 271 of the piston andthe moveable sleeve 33. A first end 277 a of the piston spring 277 is incontact with the bottom 271 b of the head 271 of the piston 270 and thesecond end 277 b of the piston spring 277 is in contact with a topsurface 35 of the inner flange 34 of the moveable sleeve 33.

A sleeve spring 278 is present between the moveable sleeve 33 and thefixed sleeve 30, with a first end 278 a of the sleeve spring in contactwith a bottom surface 36 of the flange 34 of the moveable sleeve 33 anda second end 278 b of the sleeve spring 278 in contact with the fixedsleeve 30.

A sleeve pressure chamber 276 is formed between the bore 202 a, thefixed sleeve 30 and a bottom end surface 39 of the moveable sleeve 33.The sleeve pressure chamber 276 is in fluid communication with an oilpressure supply 207 through a supply line 212 containing a check valve210. The supply 207 supplies fluid to the sleeve pressure chamber 276 tomake up for any leakage that may occur. The check valve 210 prevents anyfluid in the sleeve pressure chamber 276 from entering back into thesupply 207.

The chamber 279 present between the fixed sleeve 30, the sleeve spring278, and a bottom surface 36 of an inner flange 34 of the moveablesleeve 33 is at atmosphere. Any fluid that may be present in the chamber279 may leak through the clearances present between the inner flange 34and the shaft 272 of the piston 270.

The stiffness of the piston spring 270 is greater than the stiffness ofthe sleeve spring 278, since ideally the average length of the pistonspring 277 is unchanging as the chain length increases.

When the tensioner is tensioning a new chain, during operation, fluid issupplied to the piston pressure chamber 274 from an inlet supply line206 and optionally through an inlet check valve (not shown) topressurize the piston pressure chamber 274 and bias the piston 270outward from the housing 202 in addition to the spring force from pistonspring 277, to bias a span of the closed loop chain similar to FIG. 14a.

When the tensioner is tensioning a worn chain, without high load, duringoperation, fluid is supplied to the piston pressure chamber 274 from aninlet supply line 206 and optionally through an inlet check valve topressurize the piston pressure chamber 274 and bias the piston 270outwards from the housing 202 in addition to the spring force from thepiston spring 277, to bias a span of the closed loop chain. As the chainwears, the piston 270 has to be biased further outwards from the housing202 in order to adequately tension the chain and the moveable sleeve 33moves outwards also as indicated by the dashed-dot line moveable sleeveand similar to FIG. 14 b.

When the tensioner is tensioning a worn chain during high chain load,during operation, the high force pushes the piston 270 inwards towardthe housing 2 from the piston position shown in FIG. 14b (indicated bythe dashed lines). The inward force and the motion of the piston 270 isresisted by the fluid in the sleeve pressure chamber 276, since thecheck valve 210 in supply line 212 blocks fluid from exiting the sleevepressure chamber 276, essentially pressurizing the sleeve pressurechamber 276. The pressurization of sleeve pressure chamber 276 causesinner flange 34 of the moveable sleeve 33 to exert an outward force onthe piston 270 through the piston spring 277, opposing the inward force.Once the high load is removed from the piston 270, essentiallydepressurizing the sleeve pressure chamber 276, supply 207 suppliesfluid through the check valve 210 and supplies fluid to the fluidchamber sleeve pressure chamber 276 to fill the sleeve pressure chamber276 and compensate for the movement of the sleeve 33 relative to thepiston 270 and to maintain the position of the sleeve 33 relative to thepiston 270.

Movement of the moveable sleeve 33 moves the second end 277 b of thepiston spring 277 biasing the piston 270 outwards from the housing 202,and therefore the spring force acting on the piston 270 is variable andthe piston 270 continually tensions the chain, even when the chainbecomes worn and stretched.

Hydraulic stiffness of the tensioner is created by piston pressurechamber 274 and sleeve pressure chamber 276 of the tensioner andsubstantially prevents inward movement of piston 270 and the moveablesleeve 33 towards the housing 202 when the chain span is under load.

FIGS. 18a-18c show a tensioner under various chain condition; FIG. 18ais tensioning a new chain; FIG. 18b is tensioning a worn chain withouthigh loads; FIG. 18c is tensioning a worn chain under high load.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with first diameterportion D1 and a second diameter portion D2, with the second diameterportion D2 being larger than the first diameter portion D1.

Received within the first diameter portion D1 of the piston bore 2 a isan internal hollow piston 323 having an open end with a bottom surface323 b, a closed end with a top surface 323 d and a hollow interior 323 awith an inner diameter 323 c. Received within the bore 2 a of thehousing 2 is an internal piston spring 345 with a first end 345 a incontact the interior 323 a of the internal hollow piston 323 and asecond end 345 b of the internal piston spring 345 is in contact withthe bottom 2 c of the bore 2 a of the housing 2. The internal pistonspring 345 provides a bias force to reduce the control force required tokeep the internal piston 323 in the desired position relative to anexternal piston 303.

Received within the second diameter portion D2 is an external piston303. The external piston 303 has a body 303 a with a head 303 b incontact with a tensioner arm or guide, a bottom 303 c with a length 303d extending between the head 303 b and the bottom 303 c. Surrounding thelength 303 d of the external piston 303 is a cylinder 330 with a firstend 330 a and a second end 330 b.

A cylinder bias spring 306 is present in the second diameter portion D2of the housing 302 between a bottom 2 d of the second diameter portionD2 and the second end 330 b of the cylinder 330. A cylinder pressurechamber 307 is formed by the second diameter portion D2, the cylinderbias spring 306, and a portion of the length 303 d of the externalpiston 303. The cylinder pressure chamber 307 is in fluid communicationwith an oil pressure supply 310 through a supply line 312 containing acheck valve 311. The supply 310 supplies fluid to the cylinder pressurechamber 307 to make up for any leakage that may occur. The check valve311 prevents any fluid in the cylinder pressure chamber 307 fromentering back into the supply 310.

An external piston spring 304 is present in the second diameter portionD2 of the housing 2 with a first end 304 a in contact with a surface ofthe head 303 b of the external piston 303 and a second end 304 a incontact with the second end 330 a of the cylinder 330. The externalpiston spring 304 has a greater spring stiffness than the cylinder biasspring 306.

It should be noted that the chamber formed by the second diameterportion D2, the first end 330 a of the cylinder 330 and the head 303 bof the external piston 303 is preferably at atmosphere or atmosphericpressure.

A piston pressure chamber 316 is formed between the first diameterportion D1 of the housing 2, the interior 323 a of the internal hollowpiston 323, the internal piston spring 345, and the bottom 2 c of thebore 2 a of the housing 2.

At the bottom 2 c of the bore 2 a an inlet check valve may be present(indicated by box 308) as well as an inlet supply line 314 to provideoil pressure to the piston pressure chamber 316. The supply 310providing fluid to the cylinder pressure chamber 307 may be the same asthe supply providing fluid to inlet supply line 314. Alternatively, thesupply supplying fluid to the inlet supply line 314 may be differentthan the supply 310 in fluid communication with piston pressure chamber316.

Leakage can be created or controlled in the piston pressure chamber 316using a pressure relief valve 321 as shown or a vent, a tortuous path ora clearance path. The leakage creates damping for the external piston303.

It should be noted that the internal piston spring 345, the pressurerelief valve 321 and the internal piston 323 are preferably presentwithin the tensioner but may be removed and the tensioner still tensionsthe chain during new, worn with high loads and worn with low loadconditions.

When the tensioner is tensioning a new chain, for example as shown inFIG. 18a , during operation, fluid is supplied to the piston pressurechamber 316 from inlet supply line 314 through a check valve 308 topressurize the piston pressure chamber 316 and bias the external piston303 outward from the housing 2 in addition to the spring force from theexternal piston spring 304, to bias a span of the closed loop chain. Ifthe internal piston 323 and the internal piston spring 345 are presentin the tensioner, the force of the internal piston spring 345 as well asthe internal piston 323 would also aid in biasing the external piston303 outward from the housing 2 to bias a span of the closed loop chain.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 18b , without high load, during operation, fluid is supplied to thepiston pressure chamber 316 from inlet supply line 314 and through acheck valve 308 to pressurize the piston pressure chamber 316 and biasthe external piston 303 outward from the housing 302 in addition to thespring force from the external piston spring 304, to bias a span of theclosed loop chain. Again, if the internal piston 323 and the internalpiston spring 345 are present, the internal piston spring 345 biases theinternal piston 323 in addition to bias the external piston 303 outwardsfrom the housing 2. As the chain wears, the external piston 303 has tobe biased further outwards from the housing 2 in order to adequatelytension the chain. The additional distance that the external piston 303needs to be biased outwards from the housing 2 is provided by movementof the cylinder 330, which also moves the second end 304 b of theexternal piston spring 304 outwards from the housing 2 as well. Thecylinder 330 is moved by pressurizing the cylinder pressure chamber 307through oil from supply 310 and by cylinder bias spring 306.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 18c , during operation, the high forcepushes the external piston 303 inwards toward the housing 2 from thepiston position for example shown in FIG. 18b (indicated by dashedlines). The inward force and motion of the external piston 303 isresisted by the fluid in the cylinder pressure chamber 307, since thecheck valve 311 in supply line 312 blocks fluid from exiting thecylinder pressure chamber 307, essentially pressurizing the cylinderpressure chamber 307. The pressurization of the cylinder pressurechamber 307 causes the cylinder 330 to exert an outward force on theexternal piston 303 through the external piston spring 304, opposing theinward force. Once the high load is removed from the piston 303,essentially depressurizing the cylinder pressure chamber 307, supply 310supplies fluid through the check valve 311 and supplies fluid to thecylinder pressure chamber 307 to fill the cylinder pressure chamber 307and fluid is also supplied to the piston pressure chamber to compensatefor the movement of the cylinder 330 relative to the external piston 303and to maintain the position of the cylinder 330 relative to theexternal piston 303.

Movement of the cylinder 330 moves the second end 304 b of the externalpiston spring 304 biasing the external piston 303 outwards from thehousing 2 changing the spring bias force, and therefore the spring forceacting on the external piston 303 is variable and the external piston303 continually tensions the chain, even when the chain becomes worn andstretched. In other words, the cylinder 330 automatically adjusts theexternal piston spring 304 preload force.

Hydraulic stiffness of the tensioner is created by pressure in thecylinder pressure chamber 307 and piston pressure chamber 316 of thetensioner and substantially prevents inward movement of external piston303 and the cylinder 330 towards the housing 2 when the chain span isunder load.

Damping may be added to the tensioner by adjusting the leakage of thepiston pressure chamber 316 through the pressure relief valve 321 orother venting.

A seal or partial seal may be present between the internal piston 323and the bore 2 a and between external piston 303 and cylinder 330.

The tensioner of FIGS. 18a-18c automatically adjusts the mean tensionerforce to keep the chain tension as low as possible without sacrificingchain control, significantly improving drive efficiency at new chain andat conditions with low dynamic loads.

FIGS. 19a-19c show a tensioner under various chain condition; FIG. 19ais tensioning a new chain; FIG. 19b is tensioning a worn chain withouthigh loads; FIG. 19c is tensioning a worn chain under high load.

The tensioner is comprised of a housing 402 having an axially extendingpiston bore 402 a. The piston bore 402 a has an interior with firstdiameter portion D1 and a second diameter portion D2. The seconddiameter portion D2 being larger than the first diameter portion D1.

A hollow external piston 403 has a body with a first diameter portionand a second diameter portion. The first diameter portion of the body ofthe external piston 403 is received in the first diameter portion D1 ofthe housing 402 and the second diameter portion of the body of theexternal piston 402 is received within the second diameter portion D2 ofthe housing 402. The hollow external piston 403 has an open end with abottom surface 403 b, a transition surface 403 c between the firstdiameter portion and the second diameter portion of the body, a closedend with a top surface 403 a, and a hollow interior 403 d with an innerdiameter 403 f. The top surface 403 a of the external piston contactsand tensions a span of the chain. The external piston 403 may contactthe span of the chain through a tensioner arm.

Received within the interior diameter 403 f of the external piston 403is an internal hollow piston 423. The internal hollow piston 423 has anopen end with a bottom surface 423 b, a closed end with a top surface423 c and a hollow interior with an inner diameter 423 a. A pressurerelief valve 421 may be present within the hollow interior 423 a of theinternal piston 423.

An internal piston spring 445 is present within the inner diameter 423 aof the internal piston 423 and the inner diameter 403 f of the externalpiston 403. The internal piston spring 445 has a first end 445 a whichcontacts the hollow interior of the internal piston 423 and a second end445 b that contacts the bottom 402 c of the bore 402 a of the housing402. The internal piston spring 445 provides a bias force to reduce thecontrol force required to keep the internal piston 423 in the desiredposition relative to the external piston 403.

An external piston spring 404 is present within the inner diameter 403 fof the external piston 403. A first end 404 a of the spring is incontact with the hollow interior 403 d of the external piston 403 andthe second end 404 b of the spring is in contact with the top surface423 c of the internal piston 423. The external piston spring 404 has agreater spring stiffness than the internal piston spring 445.

It should be noted that the chamber 409 formed by the inner diameter 403f of the external piston, the external piston spring 404, and the topsurface 423 c of the internal piston 423 is preferably at atmosphere oratmospheric pressure.

An external piston pressure chamber 432 is formed by the second diameterportion D2, the transition surface 403 c of the external piston 403, anda part of the first diameter portion of the body of the external piston403. The external piston pressure chamber 432 is in fluid communicationwith an oil pressure supply 407 through supply line 412 containing acheck valve 410. The supply 407 supplies fluid to the external pistonpressure chamber 432 to make up for any leakage that may occur. Thecheck valve 410 prevents any fluid in the external piston pressurechamber 432 from entering back into the supply 407.

An internal pressure chamber 416 is formed between the first diameterportion D1 of the housing 402, the inner diameter 423 c of the internalpiston 423, the inner diameter 403 f of the external piston 403, and thebottom 402 c of the bore 402 a of the housing 402.

At the bottom 402 c of the bore 402 a, an inlet check valve may bepresent (indicated by box 408) as well as an inlet supply line 406 toprovide oil pressure to the internal piston pressure chamber 416. Thesupply 407 providing fluid to the external piston pressure chamber 432may be the same as the supply providing fluid to inlet supply line 406.Alternatively, the supply supplying fluid to the inlet supply line 406may be different than the supply 407 in fluid communication withexternal piston pressure chamber 432.

Leakage can be created or controlled in the piston pressure chamber 432using a pressure relief valve 434 as shown or a vent, a tortuous path ora clearance path. The leakage creates damping for the external piston403.

When the tensioner is tensioning a new chain, for example as shown inFIG. 19a , during operation, fluid is supplied to the external pistonpressure chamber 432 from supply 407 through a check valve 410 topressurize the external piston pressure chamber 432 and bias theexternal piston 403 through transition surface 403 c, outward from thehousing 402 in addition to the spring force from the external pistonspring 404 and the pressure acting on the internal piston 423 from inletline 406 through the internal pressure chamber 416, to bias a span ofthe closed loop chain.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 19b , without high load, during operation, fluid is supplied to theexternal piston pressure chamber 432 from supply 407 and through a checkvalve 410 to pressurize the external piston pressure chamber 432 andbias the external piston 403 outward from the housing 402 in addition tothe spring force from the external piston spring 404, and the pressureacting on the internal piston 423 from inlet line 406 through theinternal pressure chamber 416 to bias a span of the closed loop chain.As the chain wears, the external piston 403 has to be biased furtheroutwards from the housing 402 in order to adequately tension the chain.The additional distance that the external piston 403 needs to be biasedoutwards from the housing 402 is provided by movement of the internalpiston 432, which also moves the second end 404 b of the external pistonspring 404 outwards from the housing 402 as well. The tensionerautomatically adjusts the mean tensioner force to keep the chain tensionas low as possible without sacrificing chain control, significantlyimproving drive efficiency as the chain wears and is subject to lowdynamic loads.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 19c , during operation, the high forcepushes the external piston 403 inwards toward the housing 402 from thepiston position for example shown in FIG. 19b (indicated by dashedlines). The inward force and motion of the external piston 403 isresisted by the fluid in the external piston pressure chamber 432, sincethe check valve 410 in the supply line 412 blocks fluid from exiting theexternal piston pressure chamber 432, essentially pressurizing theexternal piston pressure chamber 432. The pressurization of the externalpiston pressure chamber 432 causes the internal piston 432 to exert anoutward force on the external piston 403 through the external pistonspring 404, opposing the inward force. Once the high load is removedfrom the piston 403, essentially depressurizing the external pistonpressure chamber 432, supply 407 supplies fluid through the check valve410 and supplies fluid to the external piston pressure chamber 432 tofill the external piston pressure chamber 432 and fluid is also suppliedto the internal piston pressure chamber 416 to compensate for themovement of the internal piston 432 relative to the external piston 403and to maintain the position of the internal piston 432 relative to theexternal piston 403.

Movement of the internal piston 432 moves the second end 404 b of theexternal piston spring 404 biasing the external piston 403 outwards fromthe housing 402 changing the spring bias force, and therefore the springforce acting on the external piston 403 is variable and the externalpiston 403 continually tensions the chain, even when the chain becomesworn and stretched. In other words, the internal piston 423automatically adjusts the external piston spring 404 preload force.

Hydraulic stiffness of the tensioner is created by pressure in theinternal piston pressure chamber 416 and external piston pressurechamber 432 of the tensioner and substantially prevents inward movementof external piston 403 and the internal piston 423 towards the housing402 when the chain span is under load.

Damping may be added to the tensioner by adjusting the leakage of theexternal piston pressure chamber 432 through the pressure relief valve434 or other venting.

A seal or partial seal may be present between the internal piston 423and the external piston 403 and between external piston 403 and bore 402a.

FIGS. 20a-20c shows a tensioner tensioning under various chainconditions; FIG. 20a is tensioning a new chain; FIG. 20b is tensioning aworn chain without high loads; FIG. 20c is tensioning a worn chain underhigh load.

The tensioner is comprised of a housing 2 having an axially extendingpiston bore 2 a. The piston bore 2 a has an interior with first diameterportion D1 and a second diameter portion D2, with the second diameterportion D2 being larger than the first diameter portion D1.

A hollow external piston 503 has a body with a first diameter portionand a second diameter portion. The first diameter portion of the body ofthe external piston 503 is received in the first diameter portion D1 ofthe housing 2 and the second diameter portion of the body of theexternal piston 503 is received within the second diameter portion D2 ofthe housing 2. The hollow external piston 503 has an open end with abottom surface 503 b, a transition surface 503 c between the firstdiameter portion and the second diameter portion of the body, a closedend with a top surface 503 a, and a hollow interior 503 d with an innerdiameter 503 e. The top surface 503 a of the external piston 503contacts and tensions a span of the chain. The external piston 503 maycontact the span of the chain through a tensioner arm.

Received within the interior diameter 503 e of the external piston 503is an internal piston 232 with a first end 232 a and a second end 232 b.Received within the bore 2 a of the housing 2 is an internal pistonspring 245 with a first end 245 a in contact with the second end 232 bof the internal piston 232. The second end 245 b of the internal pistonspring 245 is in contact with the bottom 2 c of the bore 2 a of thehousing 2. The internal piston spring 245 provides a bias force toreduce the control force required to keep the internal piston 232 in thedesired position relative to an external piston 503.

An internal piston pressure chamber 248 is formed between the interiorof the bore 2 a with first diameter portion D1, the bottom 2 c of thebore 2 a, the internal piston spring 245, and the second end 232 b ofthe internal piston 232.

An external piston pressure chamber 249 is formed between the interiorof the bore 2 a with second diameter portion D2, an outer surface of theinternal piston 232, and an end 503 b of the external piston 503. Theexternal piston pressure chamber 249 is in fluid communication with anoil pressure supply 207 through a supply line 212 containing a checkvalve 210. The supply 207 supplies fluid to the external piston pressurechamber 249 to make up for any leakage that may occur. The check valve210 prevents any fluid in the external piston pressure chamber 249 fromentering back into the supply 207. The external piston pressure chamber249 may also be in communication with a pressure relief valve 234.

The internal piston 232 is slidably received within the external hollowpiston 503. Also present within the external hollow piston 503 is apiston spring 204 biasing the piston 503 outwards from the housing 2.The piston spring 204 has a first end 204 a in contact with the interior503 d of the external hollow piston 503 and a second end 204 b incontact with a first end 232 a of the internal piston 232. The pistonspring 204 has a greater spring stiffness than the internal pistonspring 245. It should be noted that a chamber 209 formed between theinterior 203 a of the hollow external piston 503, the piston spring 204,and the internal piston 232 is preferably at atmosphere. Furthermore, avent may be present within the external hollow piston 503.

At the bottom 2 c of the bore 2 a an inlet check valve may be present(indicated by box 208) as well as an inlet supply line 206 to provideoil pressure to the internal pressure chamber 248. The supply 207providing fluid to the external piston pressure chamber 249 may be thesame as the supply providing fluid to inlet supply line 206.Alternatively, the supply supplying fluid to the inlet supply line 206may be different than the supply 207 in fluid communication withexternal piston pressure chamber 249.

When the tensioner is tensioning a new chain, for example as shown inFIG. 20a , during operation, fluid is supplied to the external pistonpressure chamber 249 from supply 207 through a check valve 210 topressurize the external piston pressure chamber 249 and bias theexternal piston 503 outward from the housing 2 in addition to the springforce from the external piston spring 204, to bias a span of the closedloop chain. Some force is also provided by the fluid in the internalpressure chamber 248 acting against the bottom surface 503 b of theexternal piston 503.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 20b , without high load, during operation, fluid is supplied to theexternal piston pressure chamber 249 from supply 207 and through a checkvalve to pressurize the external piston pressure chamber 249 and biasthe external piston 503 outward from the housing 2 in addition to thespring force from the external piston spring 204, to bias a span of theclosed loop chain. Some force is also provided by the fluid in theinternal pressure chamber 248 acting against the bottom surface 503 b ofthe external piston 503. As the chain wears, the external piston 503 hasto be biased further outwards from the housing 2 in order to adequatelytension the chain. The additional distance that the external piston 503needs to be biased outwards from the housing 2 is provided by movementof the internal piston 232, which also moves the second end 204 b of theexternal piston spring 204 outwards from the housing 2 as well.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 20c , during operation, the high forcepushes the external piston 503 inwards toward the housing 2 from thepiston position for example shown in FIG. 20b (indicated by dashedlines). The inward force and motion of the external piston 503 isresisted by the fluid in the external piston pressure chamber 249, sincethe check valve 210 in supply line 212 blocks fluid from exiting theexternal piston pressure chamber 249, essentially pressurizing theexternal piston pressure chamber 249. The inward force also pressurizesthe internal piston pressure chamber 248 and causes the internal piston232 to exert an outward force on the external piston 503 through theexternal piston spring 204, changing the bias force of the externalpiston spring 204 and opposing the inward force. Once the high load isremoved from the piston 503, essentially depressurizing the externalpiston pressure chamber 249, supply 207 supplies fluid through the checkvalve 210 and supplies fluid to the external piston pressure chamber 249to fill the external piston pressure chamber 249 and exert an outwardforce on the external piston 503. Fluid is also supplied from inlet line206 to compensate for the movement of the internal piston 232 and tomaintain the position of the internal piston 232 relative to theexternal piston 503.

Movement of the internal piston 232 moves the second end 204 b of theexternal piston spring 204 biasing the external piston 503 outwards fromthe housing 2 changing the spring bias force, and therefore the springforce acting on the external piston 503 is variable and the externalpiston 503 continually tensions the chain, even when the chain becomesworn and stretched.

A seal or partial seal may be present between the internal piston 232and the external piston 503 and between external piston 503 and bore 202a.

Hydraulic stiffness of the tensioner is created by pressure in theinternal piston pressure chamber 245 and external piston pressurechamber 249 of the tensioner and substantially prevents inward movementof external piston 503 and the internal piston 232 towards the housing232 when the chain span is under load.

Leakage can be created or controlled in the piston pressure chamber 249using a pressure relief valve 234 as shown or a vent, a tortuous path ora clearance path. The leakage creates damping for the external piston503.

FIGS. 21a-21c shows a tensioner tensioning under various chainconditions; FIG. 21a is tensioning a new chain; FIG. 21b is tensioning aworn chain without high loads; FIG. 21c is tensioning a worn chain underhigh load.

The tensioner has a housing 2 having an axially extending piston bore 2a. Received within the bore 2 a of the housing 2 is an inner cylinder663. The inner cylinder 663 has an inner diameter 669 and a hole 663 awhich receives a check valve 664 in the opening 663 a.

Also present in the piston bore 2 a is an external piston 603 having anopen end with a bottom surface 603 b, a closed end with a top surface603 a and a hollow interior 603 d with an inner diameter 603 c.

Received within the inner diameter 603 c of the external piston 603 isan internal piston 623 having an open end with a bottom surface 623 b, aclosed end with a top surface 623 d and a hollow interior 623 a with aninner diameter 623 c. It should be noted that piston 623 may also besolid. An internal piston spring 645 is present within the innerdiameter of the internal hollow piston 623. The first end of theinternal piston spring 645 is in contact with the hollow interior 623 aand a second end of the internal piston spring 645 is in contact with anouter surface of the inner cylinder 663. The internal piston spring 645provides a bias force to reduce the control force required to keep theinternal piston 623 in the desired position relative to the externalpiston 603.

An external piston spring 604 is present in the inner diameter of theexternal piston 603 with a first end 604 a in contact with the hollowinterior 603 d of the external piston 603 and a second end 604 b incontact with the a top surface 623 d of the internal piston 623. Theexternal piston spring 604 has a greater spring stiffness than aninternal piston spring 645.

An external piston pressure chamber 632 is formed between the bottomsurface 603 b of the external piston 603, the inner diameter of the bore2 a, and an outer surface of the inner cylinder 663. The external pistonpressure chamber 632 is in fluid communication with an oil pressuresupply 607 through supply line 612 containing a check valve 610. Thesupply 607 supplies fluid to the external piston pressure chamber 632 tomake up for any leakage that may occur. The check valve 610 prevents anyfluid in the external piston pressure chamber 632 from entering backinto the supply 607.

An internal piston chamber 616 is formed between the hollow interior 623a of the internal piston 623 and the inner diameter 603 c of theexternal piston 603. At the bottom 2 c of the bore 2 a, an inlet supplyline 606 is present to provide oil pressure to the internal pistonpressure chamber 616. An inlet check valve may be present in theinternal piston pressure chamber 616. The supply providing fluid to theexternal piston pressure chamber 632 may be the same as the supplyproviding fluid to inlet supply line 606. Alternatively, the supplysupplying fluid to the inlet supply line 606 may be different than thesupply 610 in fluid communication with external piston pressure chamber632.

A portion of the inner cylinder 663 is received by the inner diameter603 c of the external piston 603 to separate the two high pressurechambers 632 and 616.

The chamber 609 formed between the inner diameter 603 c of the externalpiston 603 and the top surface 623 d of the internal piston 623 ispreferably at atmosphere or atmospheric pressure.

Leakage can be created or controlled in the external piston pressurechamber 632 using a pressure relief valve 634 or a vent, a tortuous pathor a clearance path. The leakage creates damping for the external piston603.

When the tensioner is tensioning a new chain, for example as shown inFIG. 21a , during operation, fluid is supplied to the external pistonpressure chamber 632 from supply 607 through a check valve 610 topressurize the external piston pressure chamber 632 and bias theexternal piston 603 through a bottom surface 603 b, outward from thehousing 2 in addition to the spring force from the external pistonspring 604, to bias a span of the closed loop chain.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 21b , without high load, during operation, fluid is supplied to theexternal piston pressure chamber 632 from supply 607 and through a checkvalve 610 to pressurize the external piston pressure chamber 632 andbias the external piston 603 outward from the housing 2 in addition tothe spring force from the external piston spring 604 and the pressurefrom the inlet line 606 in internal pressure chamber 616, to bias a spanof the closed loop chain. As the chain wears, the external piston 603has to be biased further outwards from the housing 2 in order toadequately tension the chain. The additional distance that the externalpiston 603 needs to be biased outwards from the housing 2 is provided bymovement of the internal piston 623, which also moves the second end 604b of the external piston spring 604 outwards from the housing 2 as well.The tensioner automatically adjusts the mean tensioner force to keep thechain tension as low as possible without sacrificing chain control,significantly improving drive efficiency as the chain wears and issubject to low dynamic loads.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 21c , during operation, the high forcepushes the external piston 603 inwards toward the housing 2 from thepiston position for example shown in FIG. 21b (indicated by dashedlines). The inward force and motion of the external piston 603 isresisted by the fluid in the external piston pressure chamber 632, sincethe check valve 610 in supply line 612 blocks fluid from exiting theexternal piston pressure chamber 632, essentially pressurizing theexternal piston pressure chamber 632. The inward force also pressurizesthe internal piston pressure chamber 616 and causes the internal piston623 to exert an outward force on the external piston 603 through theexternal piston spring 604, opposing the inward force. Once the highload is removed from the piston 603, essentially depressurizing theexternal piston pressure chamber 632, supply 607 supplies fluid throughthe check valve 610 and supplies fluid to the external piston pressurechamber 632 to fill the external piston pressure chamber 632 andcompensate for the movement of the internal piston 623 relative to theexternal piston 603 and to maintain the position of the internal piston623 relative to the external piston 603. Fluid is also supplied frominlet line 606 to the internal piston pressure chamber 616 to compensatefor the movement of the internal piston 623. The inner piston spring 645aids in maintaining the position of the internal piston 623 as well.

Movement of the internal piston 623 moves the second end 604 b of theexternal piston spring 604 biasing the external piston 603 outwards fromthe housing 2 changing the spring bias force, and therefore the springforce acting on the external piston 603 is variable and the externalpiston 603 continually tensions the chain, even when the chain becomesworn and stretched.

A seal or partial seal may be present between the internal piston 623and the external piston 603 and between external piston 603 and bore 2a. A seal could also be present between the external piston 603 andinner cylinder 663.

Hydraulic stiffness of the tensioner is created by pressure in theinternal piston pressure chamber 616 and external piston pressurechamber 632 of the tensioner and substantially prevents inward movementof external piston 603 and the internal piston 623 towards the housing 2when the chain span is under load.

Damping may be added to the tensioner by adjusting the leakage of theexternal piston pressure chamber 632 through the pressure relief valve634 or other venting.

FIGS. 22a-22c shows a tensioner tensioning under various chainconditions; FIG. 22a is tensioning a new chain; FIG. 22b is tensioning aworn chain without high loads; FIG. 22c is tensioning a worn chain underhigh load.

The tensioner has a housing 2 having an axially extending piston bore 2a. Received within the bore 2 a of the housing 2 is an inner cylinder763. The inner cylinder 763 is hollow and has an inner diameter 763 c,an outer diameter 763 b, and a hole 763 a which receives a check valve764 in the opening 763 a. The check valve 764 could located anywherealong the inner diameter of the inner cylinder 763. The top (as shown)is one such location. The check valve could also be located at thebottom of the inner cylinder 763 or in some intermediate location withinthe inner cylinder using a flange.

Present in the bore 2 a of the housing 2 and surrounding the outerdiameter 763 b of the inner cylinder 763 is an outer cylinder 730. Theouter cylinder has a first surface 730 a and a second surface 730 b.

Also present in the piston bore 2 a is an external piston 703 having anopen end with a bottom surface 703 b, a closed end with a top surface703 a and a hollow interior 703 d with an inner diameter 703 c. Theinner diameter 703 c of the external piston 703 receives a portion ofthe inner cylinder 763. The closed end may have a vent.

An internal piston spring 745 is present in bore 2 a of the housing 2,surrounding a portion of the outer diameter 763 b of the inner cylinder763 with a first end 745 a of the internal piston spring 745 in contactwith the second end 730 b of the outer cylinder 730 and the second end745 b of the internal piston spring 745 in contact with the bottom 2 cof the bore 2 a of the housing 2. The internal piston spring 745provides a bias force to reduce the control force required to keep theouter cylinder 730 in the desired position relative to the externalpiston 703.

An external piston spring 704 is present in bore 2 a of the housing 2and surrounds a portion of the outer diameter 763 b of the innercylinder 763 with a first end 704 a of the external piston spring 704 incontact with the bottom surface 703 b of the external piston 703 and thesecond end 704 b of the external piston spring 704 in contact with thefirst end 730 a of the outer cylinder 730. The external piston spring704 has a greater spring stiffness than the internal piston spring 745.

An outer cylinder piston pressure chamber 732 is formed between thebottom 2 c of the bore 2 a of the housing 2, the outer diameter 763 b ofthe inner cylinder 763 and the second end 730 b of the outer cylinder.The outer cylinder pressure chamber 732 is in fluid communication withan oil pressure supply 707 through supply line 712 containing a checkvalve 710. The supply 707 supplies fluid to the outer cylinder pressurechamber 732 to make up for any leakage that may occur. The check valve710 prevents any fluid in the outer cylinder pressure chamber 732 fromentering back into the supply 707.

An external piston chamber 716 is formed between the interior of theexternal piston and the top surface of the inner cylinder 723.

At the bottom 2 c of the bore 2 a is an inlet supply line 706 to provideoil pressure to bias the external piston outwards from the housing 2.The supply supplying fluid to supply 707 may be the same as the supplyproviding fluid to inlet supply line 706. Alternatively, the supplysupplying fluid to the inlet supply line 706 may be different than thesupply 707 in fluid communication with the outer cylinder pressurechamber 732.

The chamber 709 formed between the bottom surface 703 b of the externalpiston 703, the external piston spring 704, outer diameter 763 b of theinner cylinder 763, and the top surface 730 a of outer cylinder 730 ispreferably at atmosphere or atmospheric pressure.

When the tensioner is tensioning a new chain, for example as shown inFIG. 22a , during operation, fluid is supplied to the outer cylinderpressure chamber 732 from supply 707 and through check valve 710,pressurizing the outer cylinder pressure chamber 732. The pressurizationof the outer cylinder pressure chamber 732 biases the external piston703 outward from the housing 2 in addition to the spring force from theexternal piston spring 304 and any fluid in chamber 716, to bias a spanof the closed loop chain.

When the tensioner is tensioning a worn chain, for example as shown inFIG. 22b , without high load, during operation fluid is supplied to theexternal piston chamber 716 by fluid from inlet supply line 706, whichpasses through the inner diameter 763 c of the inner cylinder 763 andthrough the check valve 764 at the top of the inner cylinder 763,pressurizing the external piston chamber 716. Fluid is also supplied tothe outer cylinder pressure chamber 732 from supply 707 and throughcheck valve 710. The pressurization of the outer cylinder pressurechamber 732 and the external piston pressure chamber 716 biases theexternal piston 703 outward from the housing 2 in addition to the springforce from the external piston spring 704, to bias a span of the closedloop chain. As the chain wears, the external piston 703 has to be biasedfurther outwards from the housing 2 in order to adequately tension thechain. The additional distance that the external piston 703 needs to bebiased outwards from the housing 2 is provided by movement of theexternal cylinder 730, which also moves the second end 704 b of theexternal piston spring 304 outwards from the housing 2 as well. Theexternal cylinder 730 is moved by pressurizing the outer cylinderpressure chamber 732 through oil from supply 707 and by spring 745.

When the tensioner is tensioning a worn chain during high chain load,for example as shown in FIG. 22c , during operation, the high forcepushes the external piston 703 inwards toward the housing 2 from thepiston position for example shown in FIG. 22b (indicated by dashedlines). The inward force and motion of the external piston 703 isresisted by the fluid in the outer cylinder pressure chamber 732, sincethe check valve 710 blocks fluid from exiting the outer cylinderpressure chamber 732, essentially pressurizing the outer cylinderpressure chamber 732. The pressurization of the outer cylinder pressurechamber 732 causes the outer cylinder 730 to exert an outward force onthe external piston 703 through the external piston spring 704, opposingthe inward force. Once the high load is removed from the piston 703,essentially depressurizing the outer cylinder pressure chamber 732,supply 707 supplies fluid through the check valve 710 and supplies fluidto the outer cylinder pressure chamber 732 to fill the outer cylinderpressure chamber 732 and compensate for the movement of the outercylinder 730 relative to the external piston 703 and to maintain theposition of the outer cylinder 730 relative to the external piston 703.Fluid is also supplied to the external piston chamber 716 from inletline 706. It should be noted that the internal piston spring 745 aids inmaintaining the position of the outer cylinder relative to the externalpiston 703 also.

Movement of the outer cylinder 730 moves the second end 704 b of theexternal piston spring 704 biasing the external piston 703 outwards fromthe housing 702 changing the spring bias force, and therefore the springforce acting on the external piston 703 is variable and the externalpiston 703 continually tensions the chain, even when the chain becomesworn and stretched. The outer cylinder 730 automatically adjusts theexternal piston spring 704 preload force.

Hydraulic stiffness of the tensioner is created by pressure in the outercylinder pressure chamber 732 and the external pressure chamber 716 ofthe tensioner and substantially prevents inward movement of externalpiston 703 and the outer cylinder 730 towards the housing 2 when thechain span is under load.

Damping may be added to the tensioner by adjusting the leakage of thefirst and second pressure chambers 716, 732 through the pressure reliefvalve or vent (not shown).

A seal or partial seal may be present between the internal cylinder 763and the external piston 703 and between external piston 703 and bore 2a.

The tensioner of FIGS. 22a-22c automatically adjusts the mean tensionerforce to keep the chain tension as low as possible without sacrificingchain control, significantly improving drive efficiency at new chain andat conditions with low dynamic loads.

It should be noted that in the embodiments shown, the overlap betweenthe pistons, cylinders and bores can vary. Seals may be used to reduceleakage through clearance paths.

It should be noted that pressure relief valves may be present for eachof the external piston chambers.

Volume reduces, vents and pressure relief valves may be incorporatedinto the pistons and cylindrical bore as necessary.

The cylinder or internal piston supporting the external piston springmay be controlled with a force or position control device, for example amotor or hydraulic circuit similar to the embodiments shown in FIGS.7-8. The embodiments of FIGS. 18a-22c may also use an active controlfeedback system as shown in FIGS. 9-10, eliminating the need for tightclearances and seals.

It should be noted that the external piston in any of the embodimentsmay additionally include teeth which engage a ratchet mechanism, such aspawl or ratchet clip. The ratchet mechanism provides a hard stop for theexternal piston and tensioner arm. The ratchet mechanism may be used toprevent the external piston from retracting too much when no oil ispresent, such as a start-up condition after the engine has not beoperated for some time.

A ratchet mechanism may also be applied to the “spring base”, with“spring base” being defined as the moveable sleeve, internal piston inwhich at least a portion of which is directly adjacent the bore of thehousing or external cylinder that supports the external piston spring,which in turn supports the external piston. When the ratchet mechanismis applied to the spring base, a hard stop is provided for the springbase. Since the external piston spring is present between the springbase and the external piston, a soft stop is provided for the externalpiston.

Accordingly, it is to be understood that the embodiments of theinvention herein described are merely illustrative of the application ofthe principles of the invention. Reference herein to details of theillustrated embodiments is not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe invention.

What is claimed is:
 1. A tensioner for a passive tensioner system for tensioning a chain span or a belt, comprising: a housing having a cylindrical bore with an inner surface and a fixed sleeve coaxially within the cylindrical bore, the fixed sleeve having an end with a check valve; an external piston coaxially arranged within the cylindrical bore of the housing comprising a body having an outer end and an inner end with a hollow interior and a bottom surface, the inner end being received between the inner surface of the cylindrical bore and the fixed sleeve; an internal piston received within the hollow interior of the external piston, comprising a body having an open end and a closed end; an internal piston spring received within the cylindrical bore of the housing, having a first end in contact with the internal piston and a second end in contact with the fixed sleeve, biasing the internal piston outwards from the housing; an external piston spring for biasing the external piston outwards from the housing, the external piston spring having a first end contacting the external piston and a second end contacting the internal piston; a first hydraulic chamber formed by the hollow interior of the external piston, the internal piston and the end of the fixed sleeve, having a first fluid input; such that an inward force acting to push the external piston into the housing creates a fluid pressure in the first hydraulic chamber, causing the internal piston to move relative to the external piston, changing the outward bias force of the external piston spring on the external piston; and a second hydraulic chamber formed by the cylindrical bore of the housing and the hollow fixed sleeve and the bottom surface of the external piston, having a second fluid input with an inlet check valve, such that fluid pressure in the second hydraulic chamber exerts an outward force on the external piston, the inlet check valve opposing fluid flow from the second hydraulic chamber when an inward force is exerted on the external piston.
 2. The tensioner of claim 1, further comprising a pressure relief valve in fluid communication with the second hydraulic chamber.
 3. The tensioner of claim 1, further comprising a third chamber at atmospheric pressure, the third chamber being formed between the internal piston and the hollow interior of the external piston.
 4. The tensioner of claim 1, wherein the internal piston is hollow and further comprises a bottom surface at the open end, a hollow interior having an inner diameter; with the internal piston spring received within the hollow interior of the internal piston. 